assuming that these data reflect the population of interest, these
data can be considered symmetric.
A. Calculate the mean and median. If the values are the same, then the data are symmetric.
Q. If a set of data has 1,500 values, the 30th percentile
value will correspond to the 450th value in the data when the data
have been arranged in numerical order.
A. True. .30 x 1500 = 450. That indicates that the 450 values is the 30th percentile.
Q. A nuclear power plant produces a large amount of heat that is discharged into the water system. This heat can raise the temperature of the water system which leads to an increase in the concentration of chlorophyll-a and thus a longer growing season. To study this effect, water samples were collected monthly for one year at 3 stations and the concentration of chlorophyll-a (in milligrams per liter, mg/liter) was measured. Station 1 is closest to the source of discharge while Station 3 is furthest away. The data were used to produce the following side-by-side boxplots. What is (approximately) the largest concentration of chlorophyll-a in mg/liter for Station 2?
A. The largest concentration for Station 2 appears in March. That value is approximately 17.
Q. Suppose a study of houses that have sold recently in your community
showed the following frequency distribution for the number of bedrooms:
Bedrooms Frequency
1 1
2 18
3 140
4 57
5 11
Based on this information the mean number of bedrooms in houses that
sold is approximately 3.26. Explain?
A. The first column is the number of bedrooms, and the second column is the count or frequency, i.e., how many houses with such bedrooms. Therefore, the total number of bedrooms there are:
1x1 + 2 x18 + 3x140 + 4x57 + 5x11 = 740
You need to divide this total by the total number of houses to get the average number of bedrooms per house:
Average = 740 / (1 + 18 + 140 + 57 + 11) = 740 / 227 = 3.26
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