Please help ASAP. This is for my statistics class.

Statistics
Tutor: None Selected Time limit: 1 Day

The mean of a normal probability distribution is 60; the standard deviation is 5. (Round your answers to 2 decimal places.)

a. About what percent of the observations lie between 55 and 65?

Percentage of observations %

b. About what percent of the observations lie between 50 and 70?

Percentage of observations %

c. About what percent of the observations lie between 45 and 75?

Percentage of observations %

Oct 4th, 2015

Thank you for the opportunity to help you with your question!

Since Given that mean is 60.

& standard deviation is 5.

calculate a z-score for each of the possibilities.

z-score = actual score minus mean divided by standard deviation.

 For a: 

z-score = (55-60)/5 and (65-60)/5 which results in:

z-score of -1 and 1.

this is 1 standard deviation above and below the mean which is approximately 68% of the distribution.

For b:

z-score = (50-60)/5 and (70-60)/5 which results in:

z-score of -2 and 2.

this is 2 standard deviations above and below the mean which is approximately 95% of the distribution.

For c:

z-score = (45-60)/5 and (75-60)/5 which results in:

z-score of -3 and 3.

this is 3 standard deviations above and below the mean which is approximately 99.7% of the distribution.

the actual figures are more detailed, but these are the generally recognized rounded figures that are normally used


Please let me know if you need any clarification. I'm always happy to answer your questions.
Oct 4th, 2015

I understand what you came up with. However, those answers just simply do not work in the system. Not to mention it asks to round your answers to two decimal points.

Oct 4th, 2015

that is the accurate answers. i.e. 68%,95% &99.70%

Oct 4th, 2015

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