STAT 16 PRACTICE TEST 4

  1. In a random sample of 600 people in the North, only 160 felt that the president was doing a good job. Another random sample in the South showed 110 of 500 felt that the president was doing a good job. Construct a 79% confidence interval for the difference in true proportions from these groups..
  2. A Typing teacher wants to determine whether the mean typing speed of a certain student is different from 60 wpm. What can she conclude if in 6 one minute intervals the student typed 70, 69, 39, 87, 68, and 28 wpm. Use .05 level of significance.
  3. A sample of Forty-five Red Delicious Apples had mean sugar content of 0.4 g/oz with sd=0.04, while another sample of Sixty-Two Granny Smith had a mean sugar content of 0.37 g/oz with sd=0.05. Do the Red Delicious Apples have a higher sugar then the Granny Smith Apples? Use .05 level of significance.
  4. Page 500 10.80 part aandpart b
  5. The following data shows the number of months where 0,1,2,3 bank robberies occurred over tens years.

Number of Bank Robberies

Zero

One

Two

Three

Number of months over 10 Years

50

40

20

10

Expected Probability

.5

.3

.1

.1


At a 5% level does the sample fit the theorized expected probabilities?

 

  1. The following table gives the distribution of students according to music they prefer and their IQ.

 

High

Medium

Low

Classical

5

10

5

Rock

10

10

10

Jazz

10

10

10

Country

5

10

5

At a 5% level, test the null hypothesis that music taste and IQ are independent attributes.

 

  1. Measurements of the growth of plum trees and the number of days of sunshine for a one month period are gathered from different farms across the country

Growth

Days of sunshine

7

10

8

11

6

9

9

10

8

10

10

14

7

8

12

15

    1. Find the least-square line from which we can predict the days of sunshine from growth. Graph the regression line along with the scatter diagram.
    2. Find the correlation coefficient.

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