Chapter 9 Quiz Review

Under what circumstances is a t statistic used instead of a z-score for a hypothesis test?

• When the Population's Mean is not known

• When the population standard deviation is not known

• When then Population Parameters aren't known

• None of the Above

A sample of n = 4 students hs SS = 108. What is the variance?

• s² = 27

• s² = 28

• s² = 32

• s² = 36

A sample of n = 15 scores would produce a t statistic with df = 16.

• True

• False

Answer explanation

False. Recall the df formula for a t statistic is: n - 1. Therefore, a sample of n = 15 students would produce a df of: (15 - 1) = 14.

Which of the following correctly illustrates the formula for a sample's standard deviation?

A researcher would like to evaluate the effect of a new cold medication on reaction time. It is known that under regular circumstances the distribution of reaction times is normal with μ = 200. A sample of n = 9 participants is obtained. The average reaction time for this sample is M = 206 with SS = 648. Calculate the estimated standard error.

• s_M = 9

• s_M = 81

• s_M = 8

• s_M = 3

A sample of n = 16 individuals is selected from a population with a mean of μ = 80. Assuming this is a two-tailed test, what is the t critical value?

• t = (+/-) 2.131

• t = (+/-) 2.120

• t = (+/-) 2.145

• t = (+/-) 1.96

Answer explanation

In order to solve for t critical, we need our df: (16 - 1) = 15. Now we use our df and alpha level (α = 0.05) to find the t value of (+/-) 2.131.

According to Dr. Story, what does the “t” in t-test stand for?

• Two

• Thirty

• Three

• Twenty

Which of the following are we solving for in step 5 of t-testing?

• Estimated d

• Cohen's d

• Confidence d

• None of the above

What happens to the t-distribution as df increases?

• The distribution starts to resemble a normal curve.

• The distribution becomes skewed.

• t values simultaneously start to increase

• Nothing

Most of the time, t-tests are comparing only two means except in independent-t, where we look at three.

• True

• False

Answer explanation

False. We are AWAYS looking at two means when we are using t testing.