**IT-223 - Assignment #3**

**Question # (8): ****Use the dataset callcenter80.sav
for this question, it can be found on the class webpage. It records the
duration in seconds of telephone calls to a customer support line for a company
over a certain period of days. **

· (4) Graph the histogram for this dataset.

· (4) Report the mean and standard deviation. How many calls lasted longer than 5 minutes (300 seconds)?

**Question # (12)**:
Use the 68-95-99.7 rule to answer the problems in this question. The ACT
standardized test called has an approximately Normal distribution of scores:
N(18, 6), i.e. a mean of 18 and a standard deviation of 6.

(3) One student scores a 24. What percentile is she in? What is meant by a percentile?

(3) Find the percentage of students who score between 12 and 24.

(3) What percentage of students score between 12 and 30?

(3) Do not
use the 68-95-99.7 rule for this problem. One student is determined to
have a result in the 99^{th} percentile or better! What score must she
achieve in order to achieve her goal?

Question # (20): Use the dataset ‘ bodymass.sav' for this problem. This dataset provides the lean body mass and metabolic rate (calories burned per 24 hours) for 19 individuals.

1. (4) Using SPSS, create a scatterplot of the data.

2. (4) You suspect that lean body mass is indeed correlated with metabolic rate. Therefore, you would like to do a regression analysis so that you can predict metbolic rate from lean body mass. What statistical test should you carry out first?

3.
(8) On your scatterplot, include the regression
line. Give the correlation coefficient. Describe this scatterplot using the
terms we emphasized in class. Also describe R^{2} in terms of how it
applies to this dataset.

4. (4) Provide the regression model that predicts metabolic rate from mass.

5.
**Bonus
**(up to 3 points): What changes might you make to improve your
dataset so that you end up with a more accurate regression model(s).

**Again, submit your assignment
to COL. As will always be the case, it is due 10 minutes before class time.**