Unit 8 Practice Quiz 1
1. You are going to survey GHCHS 4800 students about their exercise habits. You are interested to know the number of
hours students spend exercising during an average week. You plan to survey 100 students.
a. What is the population of interest?
The population of interest are the 4800 GHCHS students.
b. Explain how you can select a simple random sample.
To obtain a simple random sample I will assign a lotto ticket to every student at GHCHS and then use a random
number generator to select 100 students.
c. Explain how you can select a stratified random sample.
To obtain a stratified random sample I will split the students into four groups based on their grade level. Then I will
assign random numbers to those groups and select 25 students from each strata.
d. Explain how you can select a cluster random sample.
To obtain a cluster random sample I will assign numbers to every student using a random number generator. Then I
will create 48 clusters of students consisting of 100 students and then select one group randomly.
e. Explain how you can select a systematic random sample.
To obtain a systematic random sample I will randomly assign all the students at GHCHS a number 1 through 4,800.
Then I will select every 48th student to make a survey of 100 students.
2. The percentage scores on your last 5 quiz scores are: 86%, 72%, 98%, 91%, 87%
a. Find the mean of the scores
b. Find the population standard deviation of the scores.
c. Find the interval of scores within 1 standard deviation from the mean. How many of your scores are within 1
standard deviation from the mean?
3. A cereal company makes Choco Crispy Crunch Cereal. The mean for all their boxes is 10.2 oz with a standard
deviation of 0.4 oz. The weights follow a normal distribution.
a. Approximately what percent of boxes are between 9.4 oz and 11 oz?
b. Approximately what percent of boxes are less than 9.8 oz?
c. Approximately what percent of boxes are between 10.6 oz and 11 oz?
d. Approximately what percent of boxes are greater than 11 oz?
e. I bought a box that weighed 10.7 oz. What is the z-score of this box?