In: Statistics and Probability
In a random sample of 50 college seniors, 18 indicated that they were planning to pursue a graduate degree. Find a 98% confidence interval for the true proportion of all college seniors planning to pursue a graduate degree, and interpret the result, and state any assumptions you have made.
p = x/n = 18/50 = .36
So, 98% CI has Z = 2.33, hence,
We have the CI as:
p +/- Z*sqrt(p*p'/n)
= .36 +/- 2.33*sqrt(.36*.64/50)
= 0.202 to 0.518
So, 98% CI is (0.202,0.518)
98% confidence interval is a range of values that you can be 98% certain contains the true mean of the population
i.e. (.202, .518) is the range of values that we are 98% sure that it contains the true population.
We make the following assumptions for drawing the Confidence interval: