Learning Check, Estimated variance and t

1. You don't estimate the population variance by using the sample variance directly because the sample variance

a. is usually unknown
b. is from the wrong population
c. tends to be too large
d. tends to be too small

2. Which of the following is true about t distributions?

a. There are 4 different t distributions.
b. For any given sample size, there are multiple t distributions.
c. As sample size increases, the t distribution increasingly resembles a normal curve.
d. t distributions are generally leptokurtic (light-tailed)

3. t scores are used instead of Z scores when

a. you choose a one-tailed test.
b. the population variance is unknown.
c. the sample size is less than than 30.
d. the mean for the comparison population is unknown

4. Difference scores are usually used with

a. a t test for a single sample.
b. a t test for dependent means.
c. a t test for independent means.
d. a t test for three or more samples.

***Answers below***

1. d
2. c
3. b
4. b