. Adam's average (arithmetic mean) on four tests is 80. Which of the following CANNOT be the number of tests on which he earned
2 answers:
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Answer:
a. 0.443
b. 0.023
Step-by-step explanation:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
The weight of turkeys is normally distributed with a mean of 22 pounds and a standard deviation of 5 pounds.
This means that
a. Find the probability that a randomly selected turkey weighs between 20 and 26 pounds.
This is the pvalue of Z when X = 26 subtracted by the pvalue of Z when X = 20. So
X = 26
has a pvalue of 0.788
X = 20
has a pvalue of 0.345
0.788 - 0.345 = 0.443
The answer is 0.443
b. Find the probability that a randomly selected turkey weighs below 12 pounds.
This is the pvalue of Z when X = 12. So
has a pvalue of 0.023
The answer is 0.023.