Statistics Fundamentals Unit 5 Challenge 3 with Answers

Statistics Fundamentals Unit 5 Challenge 3
The cholesterol level of children is normally distributed.




If the average cholesterol level is 194 with a standard deviation of 15, what
percentage of children have a cholesterol level lower than 199? Answers are
rounded to the nearest whole percent.
a.)
26%
b.)
74%
c.)
63%
d.)
37%
c.)Correct.
Recall to find the probability, we need to convert to a z-score and then go to
standard normal chart. We can note:




Looking at a z-table, a z-score of 0.33 corresponds with a percentage of 0.6293
or about 0.63 = 63%.

, Jason sampled 60 smokers who were questioned about the number of hours they
sleep each day. Jason wants to test the hypothesis that the smokers need less sleep
than the general public which needs an average of 7.5 hours of sleep with a population
standard deviation of 0.7 hours.




If the sample mean is 7.2 hours, what is the z-score? Answers are rounded to
the hundredths place.
a.)
0.67
b.)
-0.33
c.)
-3.32
d.)
2.67
c.)Correct.
In order to get the z-score we use the formula provided. To make things easier,
first calculate the denominator: