Answer:
0.321 is the probability that their mean printing speed of the sample is greater than 17.99 ppm.
Step-by-step explanation:
We are given the following information in the question:
Mean, μ = 17.39 ppm
Standard Deviation, σ = 4.25 ppm
Sample size = 11
We are given that the distribution of printing speed is a bell shaped distribution that is a normal distribution.
Formula:
P(printing speed of the sample is greater than 17.99 ppm.)
P(x > 17.99)

Calculating the value from the standard normal table we have,

Thus, 0.321 is the probability that their mean printing speed of the sample is greater than 17.99 ppm.
29/4 hopes this help sorry if I’m wrong
Answer:
Step-by-step explanation:
We are looking for P(58 < x < 64). We need to find the percentage to the left of the z-scores for each of these numbers. To find the z scores, use the formula:

which gives us a z-score of -1. The percentage of numbers to the left of a z-score of -1 is .1586553
Now for the other z-score:
which gives us a z-score of .5. The percentage of numbers to the left of a z-score of .5 is .69146246
The lower percentage subtracted from the higher gives the area in question:
.69146246 - .1586553 = .53280716, or as a percentage, 53.3%, choice A.