Question

Directions: For each of the following studies, state both the null and alternative hypotheses and the decision rule, then work the problem. Look up the critical value of t that would cut off the tails of the distribution. Note that each study specifies the alpha value to use and whether to use a one- or two-tailed test. Decide whether to reject or fail to reject the null and answer the question. Please copy and paste the text into a document and include your answers in bold font.

There is no sample size for the first example. I will take whatever I can get to help solve

1. Sommer (1999) investigated student satisfaction with distance learning. One group of students took Introductory Psychology over the Internet and another group took the course in the usual classroom lecture format. Students rated their satisfaction with the course on a scale from 1 (not at all satisfied) to 9 (extremely satisfied). Sommer found that students in the distance learning condition had an average satisfaction of 4.33, with a standard deviation of 2.94, whereas students in the classroom format reported a mean satisfaction of 6.67 and a standard deviation of 0.82. State your null hypothesis, use α = 0.05 for a nondirectional test, and report your critical value. Is there a difference between the groups?

2. Wilson (1999) studied impulse control in grade-school children. She studied 25 average third-graders and found a failure of impulse control 4.6 times per day, with a standard deviation of 2.1 times per day. Wilson also studied 36 third-graders diagnosed with ADHD and found that they showed failures of impulse control on average 7.2 times per day, with a standard deviation of 3.1. State your null hypothesis, use α = 0.01 for a directional test, and report your critical value. Do third-graders with ADHD have more trouble with impulse control?

Answer 1

First example

The null and alternative hypothesis

Test statistic

where

Note : We assumed n1 and n2

Now ,

Thus

degrees of freedom = 25+36-2 = 59

For with 59 df , critical value of t is , tc =2.001 (two tailed)

Since calculated value of t , I t I > tc , the result is significant

We reject H0

There is sufficient evidence to conclude that there is difference between the two groups .

Note : critical value of t from t table

Example 2

The null and alternative hypothesis

Test statistic

where

Now ,

Thus

degrees of freedom = 25+36-2 = 59

For with 59 df , critical value of t is , tc =1.67 (one tailed)

Since calculated value of t , I t I > tc , the result is significant

We reject H0

There is sufficient evidence to conclude that third graders with ADHD have more trouble with impulse control .

Note : critical value of t from t table