Exam 7: Introduction to T Tests: Single Sample and Dependent Means

You are evaluating a non-directional hypothesis at the .01 significance level using a t test for a single sample.If there are 16 people in the sample,the cutoff score (critical value)needed is __________.

Knowing that a particular laboratory decision task takes the average person 2.5 seconds,an experimenter found that 30 randomly selected 80 year olds had a mean response time of 2.7 seconds with an estimated population standard deviation of 1.4 seconds.Using the .05 significance level,is the mean response time of older people slower than the response time of people in general? a.Use the five steps of hypothesis testing. b.Sketch the distributions involved. c.Explain the logic of what you did to a person who is familiar with hypothesis testing with a known population variance and a single sample,but who knows nothing about t tests of any kind (for example,you do not need to describe the steps or logic of hypothesis testing).Be sure you explain how this problem differs from a problem with a known population variance and a single sample.Your answer should consist mainly of a thorough explanation of the characteristics of the comparison distribution and all the figuring you did to determine those characteristics.

A professor believes the students in a statistics class this term are more creative than most other students attending the university. A previous study found that students at the university had a mean score of 35 on a standard creativity test, and the current class has an average score of 40 on this scale with an estimated population standard deviation of 7. The standard deviation of the distribution of means is 1.63. -The t score is

A professor believes the students in a statistics class this term are more creative than most other students attending the university. A previous study found that students at the university had a mean score of 35 on a standard creativity test, and the current class has an average score of 40 on this scale with an estimated population standard deviation of 7. The standard deviation of the distribution of means is 1.63. -The effect size is

Before conducting a t test for dependent means on a set of pretest and posttest scores,the two sets of scores must be combined into one set of scores by figuring __________.

A professor believes the students in a statistics class this term are more creative than most other students attending the university. A previous study found that students at the university had a mean score of 35 on a standard creativity test, and the current class has an average score of 40 on this scale with an estimated population standard deviation of 7. The standard deviation of the distribution of means is 1.63. -If there were 30 students in the class and the professor wanted to test the null hypothesis described in the scenario using the 5% level of significance,the cutoff t score would be

A medium effect size (d)for a t test for dependent means is

In a t test for dependent means,15 participants are each tested twice.This makes a total of 15 "before" scores and 15 "after" scores.What are the degrees of freedom?

"Student's" t test was invented by

The difference between a t test for a single sample and a Z test for a single sample is the way

A school psychologist is using a depression inventory—on which a score of 0 indicates no depression and a score of 10 indicates severe depression—to see if the level of depression in fourth graders in a particular class of 20 students differs from that of fourth graders in general at a school. The results of previous testing indicate that fourth graders at the school usually have a score of 5 on the scale, but the variation is unknown. The current sample of 20 fifth graders has a mean depression score of 4.4. -If the unbiased estimate of the population's variance is 15,the variance of the distribution of means is

If a t test for dependent means is reported in a research article as "t (16)= 2.67,p < .05," then

If 15 participants take a pretest and a posttest and have a mean difference score of 1.5,and if the standard deviation of the comparison distribution is 0.5,the t score is

If a sample includes three individuals with scores of 2,3,and 4,the estimated population variance is

An organizational psychologist wants to know if workers' health would improve if a company gave workers extra days off.All workers take a standard physical exam twice a year and are given an overall health rating with higher scores indicating better health.The psychologist selected five workers at random,arranged to have them receive an additional 2 days off every month over the period between health exams,and then compared the health scores on the two exams.Using the .05 significance level,do the scores in the table below support the notion that having extra days off improves health? a.Use the five steps of hypothesis testing. b.Sketch the distributions involved. c.Figure the effect size and find the approximate power of this study. d.Explain the logic of what you did to a person who is familiar with hypothesis testing with a known population variance and a single sample,including understanding decision errors,effect size and power,but who knows nothing about t tests of any kind (for example,you do not need to describe the steps or logic of hypothesis testing).Be sure you explain how this problem differs from a problem with a known population variance and a single sample.Your answer should consist mainly of a thorough explanation of the characteristics of the comparison distribution and all the figuring you did to determine those characteristics.

based on the following table from a research article. -Which of the following differences were significant at the .05 level?

The process of estimating the population variance from the scores in the sample involves

If a t test for dependent means is reported in a research article as "t (38)= 3.11,p < .01," then

When carrying out a t test for dependent means with a mean difference score of 20 and a variance of the distribution of means of 25,the t score is __________.(Give a number.)

The comparison distribution in a t test for dependent means is a distribution of