Exam 9: The T Test for Independent Means

Which of the following is an example of the most common way for a t test for independent means to be reported in a research article?

For a study using a t test for independent means, with any given total number of participants, power is greatest when the participants are divided into __________ groups.

Power is greatest in a t test for independent means when the sample sizes of the two groups are unequal. (True or False)

The comparison distribution for a t test for independent means is a t distribution (as opposed to a normal curve)because:

Which of the following is the best way to reduce the variances in the distributions of means when conducting a t test for independent means?

What is the harmonic mean in a study with two groups of participants in which Group 1 has 27 individuals and Group 2 has 35 individuals?

A political scientist obtained recordings of election-night acceptance speeches of seven newly elected representatives to the U.S. Congress. She counted the number of minutes devoted to urban problems in these speeches. Four of these representatives were from rural districts. They devoted 5, 0, 3, and 4 minutes to urban problems. The other three representatives studied, who were from urban districts, devoted 11, 11, and 14 minutes to urban problems. Do these results suggest that the amount of time devoted to urban problems in acceptance speeches of newly elected representatives to the U.S. Congress differ according to whether they come from rural or urban districts? (Use the .05 level.) a. Use the five steps of hypothesis testing. b. Sketch the distribution involved. c. Figure the effect size and what you can say from a power perspective? d. Explain your results to someone who is unfamiliar with the t test for independent means.

When conducting a t test for independent means:

A study with two groups of 10 participants each, using a t test for independent means, resulted in a t of 2.21, which was significant at the .05 level. The standard way of describing this in a research article would be as follows: __________.

You take a mean from a population's distribution of means and subtract it from a mean from another population's distribution of means. You do this repeatedly many times. You would be making a(n)__________.

A team of researchers studied the effects of sleep deprivation on decay of short-term memory. Eight participants stayed in a lab for 2 days. Four were randomly assigned not to sleep during that period. The other four were allowed to sleep when they wanted to do so. At the end of the 2 days, the participants completed a short-term memory task. Here are the results: Mean Time (Seconds)for Remembering Based on these results, does sleep deprivation reduce short-term memory? (Use the.05 significance level.) a. Use the five steps of hypothesis testing. b. Sketch the distribution involved. c. Figure the effect size. What can you say from a power perspective? d. Explain what you did to a person who is familiar with the t test for a single sample but is unfamiliar with the t test for independent means.

In a t test for independent means, an effect size of __________ is considered medium. (Provide a value.)

For the following question(s): A sociologist interested in cultural differences compared women of two ethnic groups on a Role Approval Index (high scores mean high degrees of approval of one's social role). The results were as follows: Ethnic Group A: N = 15 M = 55 S² = 6.5 Ethnic Group B: N = 23 M = 51 S² = 4.5 -If the standard deviation of the distribution of the difference between means is .76, what is the t score?

If a particular sample has 36 participants and the other sample has 40 participants, the total degrees of freedom for the study is __________.

"t = (M1-M2)/ S_Difference" is used to conduct a(n)__________.

In a study of the effects of a particular drug on creativity, 15 research participants took a creativity test twice: once in a normal mental state and once under the influence of the drug. In this study, you would use a t test for __________ to analyze the results.

An important focus in the t test for independent means is the difference between the means of the two groups. (True or False)

In a t test for independent means, the square root of the variance of distribution of differences between means is known as the:

A consumer researcher wanted to know if customers really are influenced to buy more from sales clerks who smile. To test this, clerks at eight stores in a large Canadian clothing chain were given special instructions at the start of a week and then sales over the week were recorded. Four of the stores were randomly selected to have the clerks receive instructions to be especially courteous and to smile a lot. Clerks at four other stores were simply instructed to be especially courteous. Sales (in thousands of dollars)for the four stores in the smile condition were 36, 40, 36, and 44; sales for the four stores in the control condition were 40, 31, 27, and 30. Do these results suggest that customers might buy more if they encounter smiling sales clerks? (Use the .05 level.) a. Use the five steps of hypothesis testing. b. Figure the effect size and estimated power. c. Explain your findings.

In a study of the effects of smell on concentration, 20 participants performed a standard task while exposed to an unpleasant smell and another 20 participants were tested on the same task but without being exposed to the unpleasant smell. You would use a t test for __________ to analyze results.