There Are 6 Questions on This Test Adding up to a Total of 105 Points. Read All the Questions

STP 420 Test 1

NAME:______ASU ID: ______

STP 420 SUMMER 2001

Exam 1

There are 6 questions on this test adding up to a total of 105 points. Read all the questions carefully.

Honor Policy: By signing below you confirm that you have neither given nor received any unauthorized assistance on this exam.

Signature: ______

Date: ______

Directions: Please read the questions carefully and place your answer in the space

provided at the end of each question. Show all necessary working.

1.[16]Political party preference in the United States depends on the age, income, and gender of the voter. A political scientist selects a large sample of registered voters. For each voter, she records gender, age, household income, and whether they voter for the Democratic or for the Republican candidate in the last congressional election. Determine whether the following variables are categorical or quantitative.

Variables / Categorical/quantitative
Gender
Age
Household income
Voting preference in last election

2.There is some evidence that increasing the amount of calcium in the diet can lower blood pressure. In a medical experiment one group of men was given a daily calcium supplement, while a control group received a placebo (a dummy pill). The seated systolic blood pressure of all the men was measured before the treatments began and again after 12 weeks. The blood pressure distributions in the two groups should have been similar at the beginning of the experiment. Here are the initial blood pressure readings for the two groups.

Calcium group

/ Placebo group
107 110 123 129 112 111 107 112 136 102 / 123 109 112 102 98 114 119 112 110 117 130

a.[5]Make a back-to-back stemplot of these data.

b.[4]Does your plot show any major differences in the two groups before the treatments began?

c.[4]In particular, are the centers of the two blood pressure distributions close together?

3.The following table shows the distribution of students your STP 420 by level.

Class levels

/ Frequency
Freshmen / 0
Sophomore / 2
Junior / 7
Senior / 14
Graduate / 4

Total

/ 27

a.[5]Construct a bar graph for the data.

b.[4]Can you construct a pie chart for the data? Why or why not?

4.A sample of 13 students of your STP 420 class resulted in the following data when their heights in inches were recorded.

72, 64, 71, 66, 71, 75, 67, 71, 62, 65, 64, 68, 76

a.[4]Find the median height of this sample.

b.[4]Find the lower quartile.

c.[4]Find the upper quartile.

d.[4]Find the inter quartile range.

The data is presented in the form of a table below.

e.[4]Find the mean height of the data.

f.[5]Find the standard deviation of the data.

5.The scores of a reference population on the Wechsler Intelligence Scale for Children (WISC) are normally distributed with mean  = 100 and  = 15.

a.[4]What percent of this population have WISC scores below 100?

b.[4]What percent of this population have WISC scores above 140?

c.[4]What percent of this population have WISC scores between 100 and 140?

6.The sample of 13 students from your STP 420 class has the following values for height and weight.

Height / 72 / 64 / 71 / 66 / 71 / 75 / 67 / 71 / 62 / 65 / 64 / 68 / 76
Weight / 214 / 150 / 200 / 120 / 210 / 215 / 120 / 190 / 125 / 145 / 124 / 135 / 225

a.[5]Draw a scatterplot of the data.

b.[4]Does the graph imply that there is a positive association, a negative association, or no association?

c.[5]Find the equation of the straight line that best fit the data using linear regression of weight on height on your calculator.

d.[4]What is the slope of the line from (c) above? Interpret its meaning in the context of the problem.

e.[4]What is the correlation coefficient r? What does it mean?

f.[4]Using the linear equation in (c) above, predict the weight of a student who is 5 feet 9 inches.

g.[5]Find the equation of the straight line that best fit the data using linear regression of height on weight on your calculator.

STP 420 TEST 1 SUMMER 2001