Exercises. 1. Find the following confidence interval for the difference between two population means assuming that the populations of paired differences are normally

1. Find the following confidence interval for the difference between two population means assuming that the populations of paired differences are normally distributed

a) n =10 ; ; confidence level = 99 %

b) n =26 ; ; confidence level = 95 %

c) n =14 ; ; confidence level = 90 %

2. A company attempts to evaluate the potential for a new bonus plan by selecting a random sample of 5 salespersons to use the bonus plan for a week period. The weekly sales volumes before and after the bonus plan implementation shown below

Weekly sales Before	Weekly sales After

Construct a 90 % confidence estimate for the mean increase in weekly sales that can be expected if a new bonus plan is implemented.

3. A company claims that the course they offer significantly increases the writing speed of secretaries. The following table gives the scores of eight secretaries before and after they attended this course.

Before
After

Make a 90 % confidence interval for the mean of the population paired differences, where a paired differences is equal to the score before attending the course minus the score after attending the course.

4. A company sent 7 of its employees to attend a course in building self-confidence. The following table gives the scores of these employees before and after attending the course

Before
After

Construct a 95 % confidence interval for the mean of population paired differences where a paired difference is equal to the score of an employee before attending the course minus after attending this course.

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