An independent testing lab compares lifetimes of halogen bulbs and incandescent bulbs. Which test is appropriate to compare the two population means?

An independent testing lab compares lifetimes of halogen bulbs and incandescent bulbs. Which test is appropriate to compare the two population means?

• A. 1-sample t-test
• B. 2-sample t-test
• C. Z-test
• D. Paired t-test

Answer: (B)

When you want to compare the average outcomes from two independent groups, use a two-sample t-test. Here, lifetimes are measured for two separate types of bulbs, giving two independent samples. You’re testing whether the two population means differ, and the variances are typically unknown, which is exactly what the two-sample t-test handles. A Z-test is not appropriate unless you know the population variances or have very large samples; a 1-sample t-test compares a sample mean to a known value, not two groups; and a paired t-test is for matched or paired data, not independent groups.

When you want to compare the average outcomes from two independent groups, use a two-sample t-test. Here, lifetimes are measured for two separate types of bulbs, giving two independent samples. You’re testing whether the two population means differ, and the variances are typically unknown, which is exactly what the two-sample t-test handles.

A Z-test is not appropriate unless you know the population variances or have very large samples; a 1-sample t-test compares a sample mean to a known value, not two groups; and a paired t-test is for matched or paired data, not independent groups.