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Mathematics 146 homework exercises
due Tuesday, November 18, 2014
1. Weights in a distant population are normally distributed about a mean of 62 kilograms,
with a standard deviation of 4 kilograms. Calculate the weights that correspond to (a) the
10th percentile, (b) the first quartile, and (c) the median.
2. A survey of 900 randomly selected people found that 27% hated eating fish of any kind.
Construct a 97% confidence interval for the percent of the population which hates eating
fish.
3. During the first week of the quarter, the 21 people in a statistics class had a mean age of
29.63 years, with a (sample) standard deviation of 10.79 years. Assuming that ages across
the college are normally distributed, construct a 90% confidence interval for the mean age
at the college.
(use the t-distribution !)
4. A local pizza shop samples 1000 customers and determines that 70% of the customers
found their food to be excellent, with a margin of error of 3%. What is the level of confidence?
5. A sample of heights is drawn from a larger population in which heights are normally
distributed. The following heights were observed, along with the number of people with
each height:
height (cm) frequency
164
2
166
4
168
6
170
4
172
2
(a) calculate the sample’s mean height and the standard deviation of the heights.
(b) construct a 95% confidence interval for the entire population’s mean height.
(use the t-distribution for part (b) !)