MGMT 650 Fall 2016 Problem Set 3   Confidence Interval:   Compute a 95% confidence interval for the population mean, based on the sample numbers 21, 22, 33, 34, 25, 26, and 139

MGMT 650 Fall 2016 Problem Set 3

1. Confidence Interval:

Compute a 95% confidence interval for the population mean, based on the sample numbers 21, 22, 33, 34, 25, 26, and 139.

Change the last value to 29 and re-compute the confidence interval.

What is an outlier and how does it affect the confidence interval?

2. t test

The director of admissions at the University of Maryland, University College is concerned about the high cost of textbooks for the students each semester. A sample of 25 students enrolled in the university indicates that x(bar) = $315.40 and s = $43.20.

1. Using the .10 level of significance, is there evidence that the population mean is above $300?
2. What is your answers if x(bar) = $315.40, s = $75, and the .05 level of significance is used?
3. What is your answer is x(bar) = $305.11 and s = $43.20?
4. D. Based on the information in part a, what decision should the director make about the books used for the courses if the goal is to keep the cost below $300?

3. Hypothesis testing using the p value:

The hypothesis is that the mean IQ of the population is 100.  A random sample of six IQs in this population resulted in the following values: 118, 105, 112, 119, 105, and 111. Using the .05 significance level, is it possible to conclude that the mean is different from 100?

1. State the decision rule.
2. Compute the test statistic
3. What is your conclusion?
4. Use Excel to find the p-value.  What does it mean?

4. Hypothesis testing on a proportion:

The administration of UMUC is concerned that a significant number of their students are not graduating in 4 years.  One factor that may contribute to the low graduation rate after 4 years could be the number of students that change their majors after the first year at UMUC.  A nationwide study found that about 50% of first year students at any university change their major after the first year.  UMUC sampled 100 students and found that 48 had changed their major after their first year.  At the .05 level, is the proportion of students at UMUC that change their major higher than 50%?