Unit 4 Review problems

Let’s review a little…

• A sample of 6 science scores is taken from all of the science scores in SEHS. Find the standard deviation of the sample. 89, 74, 56, 97, 91, 83

• In successive games, a basketball player scored 15, 19, 23, 10, 9, and 18 points. Find the standard deviation.

14.8s=5.0s=

From the previous problem…

• If each science score was increased by 5 points, how would this affect the mean and standard deviation?– The mean would increase by 5, but the

standard deviation would remain the same

• If only 2 of the scores were increased by 5 points, how would this affect the mean and standard deviation?– The mean would increase as well as the s.d.

Choose the best sample…

• The Effingham Herald wants to know where business people in Effingham County eat lunch so they conduct a survey. Which will lead to the most representative sample?– Survey men as they enter Tractor Supply– Survey people as they enter Subway – Survey women as they enter the nail salon– Survey people as they enter Wal-Mart

*SURVEY PEOPLE AS THEY ENTER WAL-MART

The sample data set below gives the recorded speeds (in mi/h) of 5 different cars on a local highway during a week day:

69, 75, 64, 65, 64

Use this data set to find the following:

• mean

• median

• range

• IQR

• standard deviation

• variance

The lists show the number of memberships sold each month for one year by two competing athletic clubs. Compare the mean and standard

deviation for the numbers of memberships sold by the two athletic clubs.

Club A: 12, 9, 14, 6, 10, 11, 19, 6, 17, 11, 4, 13 Mean = 11, Standard deviation = 4.3

Club B: 17, 10, 22, 15, 14, 19, 4, 8, 12, 22, 20, 5 Mean =14 , Standard deviation = 6.0

Choose the correct conclusion below:

A. Club A had a higher average of sales and was more consistent with sales than Club B.

B. Club A had a higher average of sales but was not as consistent with sales as Club B.

C. Club B had a higher average of sales and was more consistent with sales than Club A.

D. Club B had a higher average of sales but was not as consistent with sales as Club A

Given the variance, find the standard deviation

• variance is 150, SD =

• variance is 100, SD =

• variance is 30, SD =

Given the standard deviation, find the variance

• SD is 25, variance =

• SD is 100, variance =

• SD is 205, variance =

Calculate the variance for the following data sets:

• 2, 4, 5, 2, 4, 1

• 10, 15, 30, 15, 20

• 12, 12, 13, 14, 15, 10

Find the mean deviation

• A student took 4 tests last nine weeks and had scores of 92, 100, 65, 87.

• A player scored the following points in 3 games 9, 12, 20, 5

In a math 2 class the mean test score is 80 and the standard deviation is 5. Assuming a normal

distribution, find the following:

• the percent of test scores less than 85

• the probability that a test score will be less than 85

• the probability that a test score falls between 70 and 95

• the percent of test scores greater than 70