# Answers to the checkpoints of chapter 2

Checkpoint 1

• Qualitative, a few categories, you can’t use it to make calculations.
• Dichotomous.
• Nominal, ordinal, interval and ratio.
• The following:
1. nominal
2. interval
3. ratio
4. ordinal
5. ratio
6. ratio
7. ordinal
8. ordinal
9. ratio
10. ordinal.

Checkpoint 2

• A number that expresses the number of observations relative to the total number of observations.
• The total percentage is 25%, the applicable percentage is 50%.

Checkpoint 3

• The objective and the measurement level
• If the trend is ascending and you want to compare categories.
•  The following:

• a.    bar chart or pie chart;

b.    histogram;

c.    dot plot or line graph;

d.    box plot;

e.    bar chart;

f.     histogram (or a bar chart) if you want to see it by “size,” otherwise a box plot if you just want to show the distribution.

Checkpoint 4

• Mode, median and mean.
• Median.
• income in dollars: mean, median or mode
income in categories: median or mode
professional group: mode
job level: median or mode
number of years in the job: mean, median or mode

Checkpoint 5

• Interquartile range for ordinal variables and for continuous variables with a skewed distribution; variance for continuous variables with a minimum interval measurement level (preferably with a symmetrical distribution).
• If you’re working with sample data (and not population data).
• The problem with quadratic measures is that they are difficult to interpret. After all, we are interpreting the square of a measure. What does that mean exactly?

Checkpoint 6

• At 1-sigma 68.27% of the observations fall within +1 and -1 of the standard deviation from the center; at 2-sigma = 95.44% and 3-sigma = 99.73%.
• 100 +/- 4 * 15, so 100 +/- 60. According to the Chebyshev’s rule, at least 94% of all IQs are between 40 and 160.
•  If your IQ falls in the 94th percentile, it means that 94% of the distribution have an IQ that is the same as or a lower than yours, and (only) 6% have an IQ that is higher than yours. In that case, you are considered to be very intelligent.
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