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The weight of a Holy Hand Grenade is known to be normally distributed with a mea

ID: 3159814 • Letter: T

Question

The weight of a Holy Hand Grenade is known to be normally distributed with a mean of 15 pounds and s standard deviation of 4 pounds. Fin the probability that the mean weight of 100 randomly selected Holy Hand Grenades is at least 14 pounds. According to recent study, six in twenty unladen European swallows have a velocity of 25 mph. How would the sample proportion be distributed if a sample of swallows is drawn of size n = 100? What is the probability that more than 20% of swallows have a velocity of 25 mph. Extra: Would the results be different with African swallows?

Explanation / Answer

1. The weight of a Holy Hand...

We first get the z score for the critical value. As z = (x - u) sqrt(n) / s, then as          
          
x = critical value =    14      
u = mean =    15      
n = sample size =    100      
s = standard deviation =    4      
          
Thus,          
          
z = (x - u) * sqrt(n) / s =    -2.5      
          
Thus, using a table/technology, the right tailed area of this is          
          
P(z >   -2.5   ) =    0.993790335 [ANSWER]

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