1.4. Measures of Spread http://www.ck12.org
Part One: Answers
- b
- a
- b
- e(Note: while the standard deviation MUST always be smaller than the range, the variance is not always
smaller than the range. It is also true that the variance is the square of the standard deviation, but some
standard deviations will get smaller when they are squared. Challenge students to find examples of data sets
that illustrate these points.) - c
- c
- d
- d
- b
- b
Part Two: Open-Ended Questions
- Erica’s grades in her statistics classes are as follows:
Quizzes: 62, 88 , 82
Labs: 89, 96
Tests: 87, 99
(a) In this class, quizzes count once, labs count twice as much as a quiz, and tests count three times. Determine the
following:
(i) mode
(ii) mean
(iii) median
(iv) upper and lower quartiles
(v) midrange
(vi) range
(b) If Erica’s 62 quiz was removed from the data, briefly describe (without recalculating) the anticipated effect on
the statistics you calculated in part a.
- Mr. Crunchy’s sells small bags of potato chips that are advertised to contain 12 ounces of potato chips. To
minimize complaints from their customers, the factory sets the machines to fill bags with an average weight of
13 ounces. For an experiment in his statistics class, Spud goes to 5 different stores, purchases 1 bag from each
store and then weighs the contents. The weights of the bags are: 13. 18 , 12. 65 , 12. 87 , 13. 32 ,and 12.93 grams.
(a) Calculate the sample mean
(b) Complete the chart below to calculate the standard deviation of Spud’s sample.