## MA 123 Sample Test 1 Spring, 2012

There are 100 points on this test.  Show all your work so that I can award partial credit if necessary.  Put your names and answers on the separate blank sheets  I will pass out.

1. (50  pts total)  All parts of this problem refer to the following dataset.

 x 1 2 3 y 30 60 80
1. (10 pts) Compute the mean and standard deviation for x

2. (10 pts) Compute the mean and standard deviation for y.

3. (10 pts) Compute the correlation of the two variables.

4. (5 pts) Describe the strength and direction of the association between x and y.

5. (10 pts) Find the equation of the least-squares regression line, using x as the explanatory variable and y as the response variable

6. (5 pts) Use the equation from the previous question to predict the y value for an x value of 2.3.

2. (20 pts total—5 points each part) The following table of statistics, boxplot, and normal quantile plot were created in CrunchIt to summarize a dataset of the number of words spoken per day by the men in a study of speech patterns of 42 women and 37 men.

1. Is the distribution of the WordsPerDay variable roughly normal?  Support your answer.

2. Is the distribution of the WordsPerDay variable right-skewed, left-skewed, or not skewed?  Support your answer.

3. Are there any outliers, according to the 1.5 * IQR rule?

4. Which is a better measure of center for this data set—the mean or the median?

3. (10 pts total—5 pts each part)  Suppose a statistician told you that the distribution of the number of words per day spoken by college professors is Normal, with μ = 16,500 words and σ = 5,000 words.
1. What is the z-score for x = 15,000 words?

2. Use Table A from the textbook to calculate the percentage of college professors that speak 15,000 words per day or more.

4. (20 pts total—10 pts each part)  In a survey of two different senior level math classes at a large university, 10 of 12 in the first class claimed to rarely use a calculator when doing homework, while 13 of 17 in the second class claimed to rarely use a calculator when doing homework.
1. Summarize the data in a two-way table

2. What is the marginal distribution of rarely using a calculator when doing homework?