Measures of Center & Spread

Given the data: 136, 150, 119, 150, 125, 143.
Find the interquartile range (IQR)

•  IQR = 150 - 119 = 31

•  IQR = 150 - 125 = 25.

• IQR = 150 - 125 = 75.

•  IQR = 150 - 119 = 31.

• 13.6
• 2.2
• 15.8
• 68.2

Quartiles are values that divide a data set into four equal parts.

• True

• False

What is the standard deviation for the data given:
{12, 13, 29, 18, 61, 35, 21}

• 293.67

• 15.87

• 17.14

• 41.98

If the data set is approximately normal, what percent of people are within 1 standard deviation of the mean?

• 99.7

• 34

• 68

• 95

At a local high school, GPA's are normally distributed with a mean of 2.9 and standard deviation of 0.6. What percentage of students at the high school have a GPA between 2.3 and 3.5?

• 68%

• 99.7%

• 95%

• 84%

Which interval shows 95% of the data given a mean of 15 and a standard deviation of 3?

• 9 to 21

• 12 to 18

• 6 to 24

• 13 to 16

Which interval shows 68% of the data given a mean of 15 and a standard deviation of 3? 

• 9 to 21

• 12 to 18

• 6 to 24

• 13 to 16

Adam's Z-score on a test is +2.5.  What does this mean?

• He'd better start studying.

• He did better than EVERYONE.

• He scored 2.5 standard deviations above the average.

• He did terrible.

If Gonzalo's score is 87, the class average is 82, and the SD is 4, how many standard deviations is he above the mean?

• -1.25

• +1.25

• +1.20

• +1.02