(Questions Solutions Guide)
1. Determine if each of the following represents nominal, ordinal, interval, or ratio
data.
a. Movie ratings
b. Test scores
c. Colors of shirts
Solution: (a) ordinal data since movie ratings have an order, but cannot be subtracted;
(b) ratio data since there is a real zero; (c) nominal data as there is not even order to
these data.
2. The following numbers represent the weights in pounds of six 7- year old children in
Mrs. Jones' 2nd grade class.
{25, 60, 51, 47, 49, 45}
Find the mean; median; mode; range; variance; standard deviation.
Solution: mean = 46.17
median = 48
mode does not exist range = 35.00
variance = 134.57
standard deviation =11.60
3. If the variance is 846, what is the standard deviation?
Solution: standard deviation = square root of variance = sqrt(846) =
29.086
4. If we have the following data
34, 38, 22, 21, 29, 37, 40, 41, 22, 20, 49, 47, 20, 31, 34, 66
Draw a stem and leaf. Discuss the shape of the distribution.
Solution:
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, 2|219200
3|48714
4|0197
5|
6|6
This distribution is right skewed (positively skewed) because the “tail”
extends to the right.
5. What type of sampling technique is (a) a wheat field is divided into sections and a
random sample of stocks are taken from each section, and (b) a manufacturer
measures every 80th bottle to test for quality?
Solution: (a) stratified sample as dividing into sections and sampling the same number
from each section is a stratified sample and (b) systematic as there is a system to how
the sample is being selected.
6. If a data set with a normal distribution has a mean of 32 and a standard deviation of
4.9, what percent of the data would you expect to find between 27.1 and 36.9? What
range encompasses 99.7% of these data?
Solution: Based on the empirical rule, about 68% of the data would be within that range
as 32-4.9 = 27.1 and 32+4.9=36.9. The range to include 99.7% of the data would be
within 3 standard deviations of the mean which would be 32-3(4.9)=17.3 and
32+3(4.9)=46.7.
7. Determine the regression equation for the following data:
X: 4 5 7 3 2 7 8 9 7 6 4 6 5 9 3 2 1
Y: 9 7 8 6 9 5 6 4 3 6 7 8 9 3 4 2 4
Solution: y^ = 6.442 – 0.108x
8. If the correlation coefficient is -.749, what would be the value of the coefficient of
determination?
Solution: The coefficient of determination is (-0.749)2 = 0.561.
9. To predict the annual rice yield in pounds we use the equation
yˆ = 859 + 5.76x1 + 3.82x2 , where x1 represents the number of acres planted and
2
where x2 represents the number of acres harvested and where r = .94.
a) Predict the annual yield when 3200 acres are planted and 3000 are harvested.
2
b) Interpret the results of this r value.
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