Find the Prob.
The number of people probed by aliens in a year is normally distributed. The SD is 18 and the mean is 212. Find the prob. that less than 190 people will be probed next year.
0.11 or about 11%
Find the value of z such that 0.08 of the area lies to the left of z. Round your answer to two decimal places.
-1.41
The US Government wants to know how many Americans are abducted by aliens every year. They want to construct a 99% CI and are assuming that the population SD for the number of people abducted yearly is 20.
A 2025 study of 300 people found out that 130 had been abducted.
127.0 - 133.0
Find the area under the standard normal curve to the left of z = 2.2. Round your answer to four decimal places, if necessary.
0.9861
Men, Ray, Files
X
Mr. Gable pulls the test grades of 8 students:
60, 95, 90, 80, 80, 70, 65, 90
He wants to create a 95% CI to predict the average score of all 120 students that took the test.
Find the critical value needed to create the CI.
2.36
Find the value of z such that 0.002 of the area lies to the right of z. Round your answer to two decimal places.
2.88
A research company wants to know the consumption of Twinkies per week among males over age 30. A sample of 50 males over age 30 was drawn and the mean consumption was 50 Twinkies. Assume that the population standard deviation is known to be 12 Twinkies. Construct a 80% CI for the mean # of Twinkies.
47.8 - 52.2
Find the area under the standard normal curve between z = -0.3 and z = 0.7. Round your answer to four decimal places, if necessary.
0.3759
America, Crunch, D's
Captain
The time spent waiting in the line at fast-food place is approximately normally distributed. The mean waiting time is 7 minutes and the SD of the waiting time is 2 min. Find the probability that a person will wait between 8 to 10 minutes.
0.2471 or about 25%
Assume the heights of aliens are normally distributed. Based on a sample of 15 aliens, the mean height was 4.25 feet and the SD was 1.5 feet. Find the critical t-value needed for a 90% CI.
1.76
Assume the heights of aliens are normally distributed. Based on a sample of 100 aliens, the mean height was 4.25 feet and the SD was 1.5 feet. Construct a 95% CI for the true mean height of all aliens.
3.95 - 4.55,
or about 3 ft, 11 in to 4 ft, 6 in
The average number of Skittles in a bag is 63. The bags are normally distributed with a SD of 1.2.
Find the probability of a bag having more than 65 Skittles.
0.048 or 5%
Super, Toilet, Iron
Bowl
PS5 controllers stay charged for 8 hours on average. The charge time is normally distributed with a SD of 45 minutes.
What is the probability of a controller dying in under 6.5 hours?
0.023 or about 2%
Suppose male height is normally distributed with a mean of 5 ft, 9 in; and a standard deviation of 5 in. A university plans to recruit basketball players whose heights are in the top 10%. What is the minimum height required for recruitment?
6.3 ft or about 6 ft, 4 in
Mr. Gable pulls the test grades of 8 students:
60, 95, 90, 80, 80, 70, 65, 90
He wants to create a 95% CI to predict the average score of all 120 students that took the test.
68.1 - 89.4
Mr. Gable pulls the test grades of 8 students:
60, 95, 90, 80, 80, 70, 65, 90
He wants to create a 95% CI to predict the average score of all 120 students that took the test.
How could I improve the CI?
Raise the CI; Larger Sample/DF
King, Strange, Universe
Steven
A soft drink machine outputs a mean of 32 ounces per bottle. The machine's output is normally distributed with a standard deviation of 0.5 ounces. What is the probability of overfilling a 34 ounce bottle?
0.0 or 0%
Find the area under the standard normal curve to the left of z = -2.27 and to the right of z = 1.41. Round to 4 decimal places.
0.0909
Mr. Gable pulls the test grades of 5 students:
60, 95, 90, 80, 70
He wants to create a 95% CI to predict the average score of all 120 students that took the test. The standard deviation for all 120 students is 10.
70.2 - 87.8
What does the % of a confidence interval mean?
1) How confident you are that the interval contains the "true" mean
2) The % of intervals created from samples that would contain the "true" mean
Day, Lantern, Bay
Green