Stats without Tears
Solutions for Chapter 2
Updated 5 June 2014
(What’s New?)
Copyright © 2013–2023 by Stan Brown, BrownMath.com
Updated 5 June 2014
(What’s New?)
Copyright © 2013–2023 by Stan Brown, BrownMath.com
There’s no scale to interpret the quantities. And if one fruit in each row is supposed to represent a given quantity, then banana and apple have the same frequency, yet banana looks like its frequency is much greater.
90% of 15 is 13.5, 80% is 12, 70% is 10.5, and 60% is 9.
Score | Grade | Tallies | Frequency |
---|---|---|---|
13.5–15 | A | || | 2 |
12–13.4 | B | | | 1 |
10.5–11.9 | C | |||| | 5 |
9–10.4 | D | ||| | 3 |
0–8.9 | F | |||| | 4 |
Alternatives: Instead of a title below the category axis, you
could have a title above the graph. You could order the grades from
worst to best (F through A) instead of alphabetically as I did here.
And you could list the class boundaries as 13.5–15,
12–13.5, 10.5–12, and so on, with the understanding
that a score of 12 goes into the 12–13.5 class, not the
10.5–12 class. (Data points “on the cusp” always go
into the higher class.)
(a) The variable is discrete, “number of deaths in a
corps in a given year”.
(b)
Alternatives: Some authors would draw a histogram (bars
touching) or even a pie chart. Those are okay but not the best choice.
Commuting Distance 0 | 5 9 8 1 1 | 5 2 2 1 9 6 2 8 7 6 5 7 2 | 3 2 6 1 6 4 0 3 | 1 4 | 5 Key: 2 | 3 = 23 km |
Relative frequency is f/n. f = 25, and n = 35+10+25+45+20 = 135. Dividing 25/135 gives 0.185185… ≈ 0.19 or 19%
skewed right
(a) See the histogram at right. Important features:
(b) 480.0−470.0 = 10.0 or just plain “10”.
Don’t make the common mistake of subtracting 479.9−470.0. Subtract consecutive lower bounds, always.
(c) skewed left
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