# 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:

- nominal
- interval
- ratio
- ordinal
- ratio
- ratio
- ordinal
- ordinal
- ratio
- 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.