Question

The table below shows data from a survey about the amount of time students spend doing homework each week. The students were in either college or high school:

High Low Q1 Q3 IQR Median Mean σ
College 20 6 8 18 10 14 13.3 5.2
High School 20 3 5.5 16 10.5 11 11 5.4


Which of the choices below best describes how to measure the spread of these data?
(Hint: Use the minimum and maximum values to check for outliers.)
Both spreads are best described by the IQR.
Both spreads are best described by the standard deviation.
The college spread is best described by the IQR. The high school spread is best described by the standard deviation.
The college spread is best described by the standard deviation. The high school spread is best described by the IQR.

Answer 1

Both spreads are best described by the standard deviation

Explanation:

Answer 2

The correct option is;

Both spreads are best described by the standard deviation

Explanation:

The given information are;

, College High School

High, 20 20

Low, 6 3

Q₁, 8 5.5

Q₃, 18 16

IQR, 10 10.5

Median, 14 11

Mean, 13.3 11

σ, 5.2 5.4

Checking for outliers, we have

College

Q₁ - 1.5×IQR gives 8 - 1.5×10 = -7

Q₃ + 1.5×IQR gives 18 + 1.5×10 = 33

For high school

Q₁ - 1.5×IQR gives 5.5 - 1.5×10.5 = -10.25

Q₃ + 1.5×IQR gives 16 + 1.5×10.5 = 31.75

Therefore, there are no outliers and the data is representative of the population

From the data, for the college students, it is observed that the difference between the mean, 13.3 and Q₁, 8, and between Q₃, 18 and the mean,13.3 is approximately the standard deviation, σ, 5.2

The difference between the low and the high is also approximately 3 standard deviations

Therefore the college spread is best described by the standard deviation

Similarly for the high school students, the IQR is approximately two standard deviations, the difference between the mean, 11 and Q₁, 5.5, and between Q₃, 16 and the mean,11 is approximately the standard deviation, σ, 5.4

Therefore the high school spread is also best described by the standard deviation.