# P A A number of years ago, the road and highway maintenance department of Sin City. Nevada, began recruiting minority group members through an affirmative action program. In terms of efficiency ratings, as compiled by their superiors, how do the affirmative action employees rate? The ratings of random samples of both groups were collected, and the results are reported here (higher ratings indicate greater efficiency) Write a few sentences reporting and interpreting the results of the test. a. Sample 1 (Affirmative Action) Sample 2 (Regular) X ¯ 1 = 15.2 X ¯ 2 = 15.5 s 1 = 3.9 s 2 = 2.0 N 1 = 97 N 2 = 100

### Essentials Of Statistics

4th Edition
HEALEY + 1 other
Publisher: Cengage Learning,
ISBN: 9781305093836

### Essentials Of Statistics

4th Edition
HEALEY + 1 other
Publisher: Cengage Learning,
ISBN: 9781305093836

#### Solutions

Chapter
Section
Chapter 8, Problem 8.4P
Textbook Problem
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## P A A number of years ago, the road and highway maintenance department of Sin City. Nevada, began recruiting minority group members through an affirmative action program. In terms of efficiency ratings, as compiled by their superiors, how do the affirmative action employees rate? The ratings of random samples of both groups were collected, and the results are reported here (higher ratings indicate greater efficiency) Write a few sentences reporting and interpreting the results of the test.a. Sample 1(Affirmative Action) Sample 2(Regular) X ¯ 1 = 15.2 X ¯ 2 = 15.5 s 1 = 3.9 s 2 = 2.0 N 1 = 97 N 2 = 100

Expert Solution
To determine

To find:

The significant difference in the sample statistics of the two samples.

### Explanation of Solution

Given:

The sample statistics is given in the table below,

 Sample 1(Affirmative Action) Sample 2(Regular) X¯1=15.2 X¯2=15.5 s1=3.9 s2=2.0 N1=97 N2=100

The five step model for hypothesis testing:

Step 1. Making assumptions and meeting test requirements.

Step 2. Stating the null hypothesis.

Step 3. Selecting the sampling distribution and establishing the critical region.

Step 4. Computing test statistics.

Step 5. Making a decision and interpreting the results of the test.

Formula used:

The formula to calculate the sampling distribution of the differences in sample means is given by,

Z(obtained)=(X¯1X¯2)(μ1μ2)σX¯X¯

Where, X¯1 and X¯2 is the mean of first and second sample respectively,

μ1 and μ2 is the mean of first and second population respectively,

σX¯X¯ is the standard deviation and the formula to calculate σX¯X¯ is given by,

σX¯X¯=s21N11+s22N21

Where, N1 and N2 is the number of first and second population respectively.

Calculation:

From the given information, the sample size of the first sample is 97, the sample size of the second sample is 100, the sample mean of the first sample is 15.2, the sample mean of the second sample is 15.5, the sample standard deviation of the first sample is 3.9, and the sample standard deviation of the second sample is 2.0.

As the significant difference in the sample statistics is to be determined, a two tailed test is applied.

Follow the steps for two-sample testing as,

Step 1. Making assumptions and meeting test requirements.

Model:

Independent random samples.

Level of measurement is interval ratio.

Sampling distribution is Normal.

Step 2. Stating the null hypothesis.

The statement of the null hypothesis is that there is no significant difference in the sample s of the population. Thus, the null and the alternative hypotheses are,

H0:μ1=μ2

H1:μ1μ2

Step 3. Selecting the sampling distribution and establishing the critical region.

Since, the sample size is large, Z distribution can be used.

Thus, the sampling distribution is Z distribution.

The level of significance is,

α=0.05

Area of critical region is,

Z(critical)=±1.96

Step 4. Computing test statistics.

The population standard deviations are unknown.

The formula to calculate σX¯X¯ is given by,

σX¯X¯=s21N11+s22N21

Substitute 3

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