Identify the Inference Methods Practice Test

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• Is there evidence of a significant difference in airline flight costs between the east and west coasts to Lincoln, Nebraska? Which test is used to compare the costs of two independent regions?
• In a chi-square test of homogeneity with multiple groups and a single categorical variable, which statement is the null hypothesis?
• What is the odds ratio for death comparing depressed vs non-depressed?
• With a random sample of 800 adults, attitudes toward cloning laws are categorized by education level (high school, 2-year college, 4-year college, or advanced degree). To test whether cloning opinions are associated with education level, which test should be used?
• When the same subjects are measured under two conditions, which test should be used?
• In a study with 600 high school seniors analyzing GPA and college aid using linear regression, what is the approximate degrees of freedom for the slope test?
• An owner of a construction company wants to know if work times for room additions can be completed faster than the contract times. Which test is appropriate to analyze the evidence?
• In Landon et al. (2009), 958 women with mild gestational diabetes were randomized to usual care or treatment. Among the control group, 68 babies were LGA; among the treatment group, 29 were LGA. Which test would compare these proportions?
• A researcher compares blood pressures of 40 vegetarians and 40 meat-eaters to see if diet affects blood pressure. Which test is appropriate?
• In a 1973 lawsuit, admissions data were collected on two graduate programs by gender. To test whether admission proportions differ by gender across programs, which statistical test is appropriate?
• If p-value < 0.05, what conclusion?
• Which group had a higher death count in absolute numbers?
• Which test is appropriate to assess if observed counts across several categories fit a specified distribution?
• In a simple linear regression analyzing the relationship between candy amount and blood sugar levels, what does Ho: B1 = 0 represent?
• A NYC mayoral candidate asks voters from two boroughs about approval of Stop and Frisk. Do approval rates vary between Queens and Brooklyn?
• Which statistic is appropriate to compare mortality proportions between the depressed and non-depressed groups?
• A wildlife biologist wants to determine the mean weight of adult red squirrels. She weighs 10 squirrels and records a mean of 12.32 grams and a standard deviation of 1.88 grams. Which method would be used to construct a confidence interval for the mean?
• Which test is equivalent to the 2-proportion z-test when comparing two independent proportions with large samples?
• A random sample of 88 students found 14 who cheated; to test whether the true cheating rate is greater than 0.10, which statistical test should be used?
• In a randomized trial comparing AZT during pregnancy to placebo, researchers compared the proportion of births in which the baby was HIV-positive between the two groups. Which statistical test is most appropriate for comparing these two proportions?
• Researchers compare the number of fractures treated in January and July across 25 emergency rooms. Which test is appropriate for these paired measurements?
• A 2009 survey reported that 63% of dog owners and 53% of cat owners would be at least somewhat likely to give CPR to their pet. Which statistical test is appropriate to compare these two proportions?
• A random sample of 20 beat cops yields a mean salary of 51,300 with a standard deviation of 1,900. Which inferential test is appropriate to assess whether the true mean salary is less than 52,000?
• In a study examining four bathroom stalls, which statistical test would determine if stalls are used with equal frequency?
• A health researcher samples patients from two clinics to compare their average wait times. What statistical test should be used to compare the mean wait times?
• In a chi-square test of independence with 4 education levels and 3 opinion categories, what are the degrees of freedom?
• During a trial with 18 employees, the average product packed increases by more than 10 cases per day per employee. The appropriate test is which of the following?
• Which interval estimate would be used to estimate the population proportion of successes from a sample?
• According to United Nations Population Division, the age distribution of the Commonwealth of Australia is: 21% less than 15 years of age, 67% between 15 and 65 years of age, and 12% over 65. A random sample of 210 Canberra residents revealed 40 under 15, 145 between 15 and 65, and 25 over 65. Are the ages of Canberra residents unusual in any way?
• A coffee house weighs 10 cups of coffee for customers and finds a mean of 12.5 ounces and a standard deviation of 0.5 ounces. Assuming these cups are a random sample of all cups, which method would be used to estimate the mean weight of all cups?
• A psychologist studies whether a therapy program changes average anxiety scores. Patients are measured before and after treatment. Which test is appropriate?
• What is the overall death rate in the study?
• To estimate the road test failure rate, a random sample of 65 student drivers is used, among whom 37 failed at least once. Which interval method should be used?
• Do age groups and planned Facebook time have independent distributions? Which test is appropriate?
• To compare adoption rates between men and women using two proportions, which test is appropriate?
• Investigators at an agricultural research facility randomly assigned equal numbers of chickens to be housed in two rooms. In one room, normal day/night cycles; in the other, lights on 24 hours a day. Is there evidence that chickens will lay more eggs when lights are always on?
• How many total deaths occurred in the study?
• In a study of teachers, 150 were surveyed and 72% volunteered to a local charity in the past year. Which inference method should be used to test whether the population proportion of volunteers is less than 0.75?
• Which test would determine whether there is an association between gender and whether or not college-age drivers were ticketed?
• A soccer player sets a goal to improve his kicking accuracy from 50%. After 12 kicks, he makes 10. Which test is appropriate to assess this proportion?
• At a roadblock, tickets were issued for expired inspection stickers to 22 of 628 cars stopped. Based on this sample, estimate the proportion of autos in the region with expired inspections.
• Forty teenagers ate candy; one hour later their blood sugar levels were measured. Is there evidence that the amount of candy eaten is linearly associated with blood sugar levels?
• An oral surgeon records times for 24 surgeries to estimate the mean time to extract all four wisdom teeth. Which inference method is appropriate?
• A random sample of 600 high school seniors reports their GPA and the amount of financial aid offered by colleges. Which test assesses whether there is an association between GPA and college aid?
• To test whether there is a linear association between two quantitative variables, which test is used?
• What test is most appropriate for measuring the association between gender and favorite color when both variables are categorical?
• A factory foreman estimates mean daily shirts produced as 230 with standard deviation 13; he constructs a 95% confidence interval for the mean using a t-interval. Which method is used?
• A factory installed scrubbers; measurements of sulfate levels before and after installation were taken, but not paired. Which test compares the two independent samples?
• Which takes less time to travel to work - car or train? A random sample of 45 businessmen is used to compare travel times for both types of commute.
• What is the absolute difference in mortality between depressed and non-depressed?
• The Associated Press and petside.com survey (2009) found that 63% of dog owners and 53% of cat owners would be likely to give CPR to their pet. Which test would compare these two proportions?
• For a bag of peanut M&M's, observed counts for Brown 39, Yellow 44, Red 36, Blue 78, Orange 73, and Green 48. Test whether the bag's color distribution matches the official distribution.
• At one SAT test site students taking a second test inhaled supplemental oxygen for 10 minutes before the test. Some received oxygen, others did not. Which procedure should we use to test whether breathing extra oxygen improves test performance?
• A farmer would like to know if a new fertilizer increases crop yield. The farmer records the yield for 10 different fields prior to adding fertilizer and after adding the fertilizer. Which test works?
• When estimating the mean weight of stray cats using a single sample, which interval method is appropriate?
• In a chi-square goodness-of-fit test, which statement about the null hypothesis is correct?
• Many states mandate tests that have to be passed for graduation. A tutor works with 15 students for a month before the plan to implement an after-school tutoring program. The tutoring program will be implemented if student scores increase by more than 20 points. Which test should be used to analyze the before/after scores?
• A study measures baseline blood pressure, then undergoes an exercise program for a month, and blood pressure is measured again. Which test assesses whether the program changed blood pressure?
• In a regression predicting electrical usage from average monthly temperature, which test assesses whether the temperature coefficient is different from zero?
• In analyzing CTBS scores for math and reading, which test would determine if there is a linear relationship between the two quantitative scores (degrees of freedom unknown)?
• Two body shops' repair costs are compared using random samples of ten bills from each shop. Is there a significant difference in costs?
• In a study of college students, researchers test whether sex is associated with voting registration status (registered vs not). Which statistical test is appropriate?
• An orthodontist compares cement bond strength in 40 patients who do not drink soda and 40 who do drink soda.
• Researchers offer small cookies to nine nursery school children and record the number of cookies consumed by each. Forty-five minutes later they observe these children during recess, and rate each child for hyperactivity on a scale from 1 - 20. Is there any evidence that sugar contributes to hyperactivity in children?
• Two groups: homeopathic vs placebo; pain response categorized into four levels. Which test compares the distributions of responses between the two groups?
• A pollster collects data on gender (male, female) and car choice (American, Asian, European) to examine whether gender is related to car choice. Which test is appropriate?
• In a study of blood pressure, 12 subjects have their BP measured, then the drug is given and BP rechecked after one hour. The drug will be approved if there is no evidence that the average increase exceeds 20 points. Which test is used?
• Was mortality higher among those with depression?
• A manufacturing plant investigates defect types from three vendors to see if the distribution of defect types is the same across vendors. Which test is used?
• A homeowners association wants to test if 75% of residents favor an amendment; sample 310 of 430 are in favor. Which test is used?
• Suppose you compare the proportion of students showing school pride between two schools. Which test would you use to test for a difference in proportions between two independent groups?
• A car company has made an adjustment to improve gas mileage. Random samples of cars measured before and after the adjustment. Which test should be used to determine if the mean difference is zero?
• Wilt et al. (2012) studied whether surgery improves men’s survival after localized prostate cancer. After about 10 years, 21 of 364 in the surgery group and 31 of 367 in the observation group died. Which test should be used to compare these two proportions?
• Honors Graduates last year had counts from public, private, home-schooled, and abroad. Is there evidence that the distribution of high school types among Honors Graduates differs from the distribution among the rest of the college students?
• In regression results, which statement correctly characterizes the role of the t-statistic for the slope?
• An English professor surveys a random sample of her students to test whether the average score is greater than 78. Which test is appropriate?
• Sixty senior account executives are classified into three groups, A, B, and C. Testing whether the population proportions in these groups are equal uses which test?
• For a 3x2 contingency table measuring two categorical variables across a single population, which test is appropriate to assess independence?
• A policeman believes that more than 40% of older drivers speed on highways, but a confidential survey found that 49 of 88 randomly selected older drivers admitted speeding. Is this strong evidence that the policeman was wrong?
• A CDC report found arthritis among adults: 51 of 100 men and 80 of 782 women. To estimate the difference in proportions with 95% confidence, which method would you use?
• Imagine random samples of men and women are asked if they donated blood in the past 12 months. Which test would compare the proportion who donated between genders?
• In a two-sample t-test comparing lifetimes of halogen and incandescent bulbs, the null hypothesis states that the difference in means equals zero. Which statement expresses that null hypothesis?
• In comparing flea rates between dogs and cats, the null hypothesis states that the proportions are equal. Which expression represents this null hypothesis in terms of p_dogs and p_cats?
• A study comparing jail time for black and white offenders with 25 cases in each group. Which test best determines if there is a difference in average jail time between the two groups?
• A factory wants to estimate the average weight of its bottles. A random sample of 10 bottles is weighed. Which method should be used to estimate the population mean weight?
• Two dog parks in a city are studied. Dogs are categorized by size: toy, small, medium, large, and giant. Is the breed size distribution different between the two parks?
• In a study, 63 of 211 men and 130 of 651 women prefer cats to dogs. Which test assesses whether women are more likely to prefer cats?
• A friend claims he scores 1400 on a game; you collect a random sample of 12 scores; is there evidence that the population mean is less than 1400?
• In a NEJM study of mild gestational diabetes, 958 women were randomized to usual prenatal care (473) or intensive treatment (485). Among controls, 68 babies were large for gestational age (LGA), and among the treatment group, 29 were LGA. Which test should be used to compare these two proportions?
• A fitness trainer wants to know if a weightlifting program quickly improves upper body strength in people over 55. Participants perform push-ups for 90 seconds before and after a 3-week program. Which statistical test best compares the before/after measurements?
• A random sample of 22 garbage cans yields a mean of 33.2 pounds with a standard deviation of 3.2 pounds. Is there evidence that residents overload garbage cans beyond 30 pounds on average?
• Two categorical variables from a single population, test whether they are related. Which test is appropriate?
• Doctors at a technology research facility randomly assigned equal numbers of people to use standard keyboards in one room and ergonomic keyboards in another to see if ergonomic keyboards increase words per minute. Which test should be used?
• A random sample of costs for 10 different stylists was taken at Hair by Charles and Curl Up & Dye. Do the salons differ in mean costs?
• In a regression output, what does a high R-squared value represent?
• How many patients were in the depression group?
• Singer et al. (2000) investigated whether offering a monetary incentive with an advance letter would improve response rates to a telephone survey. Among those who received the incentive, 286 of 368 responded; among those who received only the advance letter, 245 of 367 responded. Which test would compare these two proportions?
• Which statement best describes adjusted R-squared in regression analysis?
• Among a random sample of college-age students, 6% of the 473 men said they had been adopted, compared to 4% of the 552 women. Which test is appropriate to determine if there is a significant difference between adoption rates by gender?
• A test used to determine if observed frequencies across four categories match an expected distribution is called the chi-square goodness-of-fit test.
• In a two-proportion z-test, when testing the equality of two proportions, you typically use a pooled estimate of p under H0. Which statement is correct?
• Record gunshot wounds in January and July from 50 emergency rooms to see if there is more gun violence in summer than winter. Which test is used to compare the two paired time periods?
• To assess whether a new sample of grades matches a historical grade distribution (A through F with specified percentages), which test is appropriate?
• In the described regression, the slope is negative and significant. Which interpretation is correct?
• For a one-sample t-test with sample size n, the degrees of freedom are:
• A study with 18 observations aims to estimate the population mean with 95% confidence. Which method should be used for the confidence interval when the population standard deviation is unknown?
• A 2013 Gallup poll asked randomly selected U.S. adults about staying at their current weight. Among 562 men, 242 wanted to stay; among 477 women, 172 wanted to stay. Which test should be used to compare these two proportions?
• What is the proportion of deaths within the depressed group?
• In October 2013, Gallup reported that 52% of U.S. adults disapprove of the Affordable Care Act, based on random samples of 450 people, up from 45% a year earlier. Is this evidence of a real change in public opinion?
• A randomized trial by Wilt et al. (2012) compared surgery versus observation for localized prostate cancer. If 21 of 364 who had surgery died and 31 of 367 in the observation group died, which test would compare these proportions?
• Which test would you use to examine whether the mean difference in paired data differs from zero?
• When assessing whether there is an association between two quantitative variables, which test provides the p-value for the slope?
• Two areas of the Comprehensive Test of Basic Skills (CTBS) were tested: math and reading. To determine if there is an association between math and reading scores, which test is used?
• Which test is used to compare the mortality proportions between the depressed and non-depressed groups in this data?
• To measure a linear relationship between two quantitative variables, which test is most appropriate?
• A survey asks whether the population proportion favors the union more than 0.60. In a sample, 74 of 120 employees favor the union. Which inference method is appropriate to test whether the true proportion is greater than 0.60?
• Females report an average of 16.8 hours studying per week, while males report 13.8 hours. Is this evidence of a difference in mean study time by gender? Which test?
• A study of large carnivores analyzes whether there is a linear association between body length (meters) and weight (kilograms). Which method should be used?
• Which statistical test is used to determine if flea rates differ significantly between dogs and cats?
• To compare jail time sentenced for bank robbers and car thieves, which test compares two independent means?
• Which test is appropriate for comparing two related samples, such as measurements on the same individuals under two conditions?
• If you want to estimate the difference between two proportions with a confidence interval, which method should you use?
• Two production lines have different defect rates. Which test would compare their defect proportions?
• Among college-age drivers, 5% of the 576 men said they had been ticketed for speeding during the past year, compared to only 3% of the 552 women. Does this indicate a significant difference between college males and females in terms of being ticketed for speeding?
• A weight study of 24 newly admitted stray cats aims to estimate their mean weight. Which method provides a confidence interval for the mean weight?
• A bank branch wants to estimate the average wait time in the teller line. Times from 40 randomly selected customers are recorded. What is the appropriate inference procedure?
• Two independent samples of exam scores from two different schools are compared to see if their means differ. Which test?
• A supermarket chain assigns 15 stores to Display Type A and 15 stores to Display Type B and records items sold per store. Which test compares the mean sales between the two independent display methods?
• Hospital nurses collected data on length of surgery (hours) and length of hospital stay (days) for 58 patients. Which test is appropriate to assess whether these two quantitative variables are related?
• In a poll, the proportion of yes responses is tested whether it equals 0.50. Which test would you use?
• Who is paid more in New York State - teachers or policemen? We select a random sample of 25 New York cities and find the starting salaries of teachers and policemen in each. Which test is appropriate?
• A national marketing campaign increases name-brand recognition. After campaign, 135 of 500 recognize the brand; baseline recognition is 0.23. Which test is appropriate to determine whether recognition increased?
• What are the null and alternative hypotheses described for the comparison?
• An industry analyst tracks weekly box office revenues for a film over 20 weeks and wants to know if there is a linear relationship between sales and time. Which inference method would be appropriate?
• Is there an association between eye color and meningitis-related deafness? Which test would be used?
• A college alumni fund compares two contact methods (phone versus email) for a random sample of alumni. In the phone group 40% donated and in the email group 30% donated, with 150 alumni in each group. The fund wishes to estimate the difference in donation proportions between the two contact methods. Which inference method is appropriate?
• What is a reasonable conclusion about the relationship between depression and mortality in cardiac disease?
• Ward's Communications reports the distribution of colors among sports car enthusiasts. A sample of 250 cars at a NASCAR raceway shows various colors. Which test assesses whether NASCAR color preferences are typical of sports car enthusiasts?
• A student weighs 10 candy bars; test whether the average weight differs from the expected value using a t-test. Which test is appropriate?
• To estimate a population mean with a small sample and unknown standard deviation, which method should be used?
• A flower pot manufacturer samples 25 pots to test whether mean thickness differs from 4 mm, with sample mean 4.3 mm. Which test should be used?
• A study compares pass rates for two teaching methods with binary outcomes. Which test should be used?
• In a sleep study, exercise reduces the proportion with difficulty sleeping: 23/100 in exercise vs 31/100 in non-exercise. Which test assesses statistically significant difference in proportions?
• In the study of school goals among students in grades 4–6, what test determines if grade level is related to the most desired school goal (make good grades, be popular, be good at sports)?
• From 10 customers, mean weight 4.5 oz, s = 0.25 oz. Assuming random sampling, which method should be used to estimate the population mean weight of all cups with a confidence interval?
• To determine if there is a linear relationship between two quantitative variables, which test would you use?
• In July 2011, Ma-Vib fired 15 of 18 women and none of the 12 men. Which test would be appropriate to assess whether layoff rates differ by gender?
• In Psychology of Music (2010), a study examined the effects of romantic lyrics on compliance with a courtship request. The female participants were randomly assigned to listen to either a romantic or a neutral song. After three minutes, a male confederate asked for their phone number. Which test would compare the proportion who provided a number across the two listening conditions?
• In a study comparing responses from 6th graders and 12th graders to a question with three possible answers, which test is appropriate to compare the distributions across the two independent groups?
• At one vehicle inspection station, 13 of 52 trucks and 11 of 88 cars failed the emissions test. Is this evidence of a difference in the percentages of all cars and trucks that are not in compliance with air quality regulations?
• In a study with a 2x2 design to test the association between group and outcome, which test would assess whether there is an association?
• In a study of how the burden of poverty varies among U. S. regions, a random sample of 1000 individuals from each of four regions was collected. Which test is appropriate to assess whether poverty levels differ by region?
• To determine whether the distribution of a categorical outcome is the same across two populations, which test is appropriate?
• Which test would be used to examine the mean difference in a paired study?
• An independent testing lab compares lifetimes of halogen bulbs and incandescent bulbs. Which test is appropriate to compare the two population means?
• What is the mortality rate among patients with depression?
• In a chi-square test of independence with five rows and two columns, what is the degrees of freedom?
• In a survey, researchers test whether eating breakfast in the morning is associated with a student’s gender. Which test is used?
• In a best-of-seven series, if both teams are equally matched, which test would assess whether the observed distribution of series lengths fits the 50-50 model?
• Among Americans, Type O 45%, Type A 40%, Type B 11%, Type AB 4%. A blood drive collected 132 pints with counts 51 O, 55 A, 17 B, 9 AB. Was this yield unusual in any way?
• A health professional sampled 100 patients from each of four major hospital emergency rooms to see if primary reasons for ER visits are similar across hospitals. Primary reasons: accident, illegal activity, illness, or other. What test evaluates whether the distribution across hospitals is the same?
• To test whether overtime occurrences are equally likely across NBA, NFL, NHL, and MLB, which inference method should be used?
• Another study investigates whether there is a linear relationship between sugar consumption and hyperactivity scores. Which test would be used?
• Which test compares the means of two independent samples for a continuous outcome?
• Are female or male students more likely to attend college outside their home state? Two independent samples of male and female college-bound students are examined to see if attending college outside Texas. Which procedure would be used to estimate whether gender is associated with attending college outside the state?
• A quality-control team wants to test whether the average wait time is 6 minutes using a large sample where the population standard deviation is known. Which test is appropriate?
• Two treatments with five possible responses; test whether the distributions across treatments are the same. Which test should be used and what are the degrees of freedom?
• Do district teachers' CCSS approval levels align with the national distribution? Which test is used?
• A study compares mean blood pressure between two clinics using random samples. Which test is appropriate to compare the means?
• What is the relative risk of death for depressed vs non-depressed?
• Two suppliers' shipments are tested for defect rates. The contract accepts the shipment with the smallest rate. Do the defect rates vary between suppliers?
• A chi-square goodness-of-fit test with three categories has how many degrees of freedom?
• Forty people with allergies take an antihistamine; they report that their discomfort subsided on average in 18 minutes with a standard deviation of 4 minutes. The goal is to estimate the population relief time. Which method is appropriate?
• To estimate the difference in mean TV viewing hours between high school and middle school students, which inference procedure is appropriate?
• To compare the proportions between two independent groups, which test would you use?
• To assess whether a new bootcamp regimen increases BMI, BMI measured for 15 clients before and after. Which test is appropriate?
• In a trial comparing two drugs, patient outcomes are categorized as 'improved', 'no change', or 'worsened'. Which test evaluates whether the distribution of outcomes is the same across the two drugs?
• A nutrition program aims to determine whether the mean change in cholesterol after the program differs from zero, using paired measurements on the same individuals. Which test?
• In a vending machine study with four drink types, the investigator asks if four types are equally favored. Which test is appropriate?
• A study reports that 22 people experienced relief with an average time of 13 minutes and a standard deviation of 4 minutes. To construct a 95% confidence interval for the population mean relief time, which method is appropriate?