Answer: a. Standard Error = 0.045
b. P (p-hat<0.33) = 0.0606
c. P (0.38<p-hat<0.46) = 0.5782
Step-by-step explanation: The sample proportion is p-hat=0.4
a. Standard error of a sample proportion is calculated as:
with p=0.4 and n=120:
SE = 0.045
The standard error of the sample proportion of students bringing their own computer is 0.045.
b. To determine the probability for sample proportions, first find the z-score:
P(p-hat < x) =
P(p-hat < 0.33) =
Now, using z-score table, find the probability:
= 0.0606
Probability the sample proportion is less than 0.33 is 0.0606.
c. For probability between two proportions, find z-score for each number of the interval:
For p < 0.38:
P(p-hat < 0.38) =
P(p-hat < 0.38) =
Using z-score table,
= 0.33
For p < 0.46:
P(p-hat < 0.46) =
P(p-hat < 0.46) = P(z < 1.33)
Probability is
P(z < 1.33) = 0.9082
The probability of the interval is the difference of each probability:
P(0.38 < p-hat < 0.46) =
P(0.38 < p-hat < 0.46) =
P(0.38 < p-hat < 0.46) = 0.5782
Probability the sample proportion is between 0.38 and 0.46 is 0.5782.