Question 1
A marketing research company is estimating which of two soft drinks college students prefer. A random sample of 341 college students produced the following 95% confidence interval for the proportion of college students who prefer one of the colas:
What additional assumptions are necessary for the interval to be valid?
◦ The sample was randomly selected from an approximately normal population.
◦ No additional assumptions are necessary.
◦ The sample proportion equals the population proportion.
◦ The population proportion has an approximately normal distribution.
Question 2
What type of car is more popular among college students, American or foreign? One hundred fifty-nine college students were randomly sampled and each was asked which type of car he or she prefers. A computer package was used to generate the printout below for the proportion of college students who prefer American automobiles.
SAMPLE PROPORTION = .396226
SAMPLE SIZE = 159
UPPER LIMIT = .46418
LOWER LIMIT = .331125
Is the sample large enough for the interval to be valid?
◦ No, the population of college students is not normally distributed.
◦ Yes, since
n
and
n
are both greater than 15.
◦ No, the sample size should be at 10% of the population.
◦ Yes, since
n > 30.
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