[Afzal]

can you explain 3.6.6- b& c and also 3.6.8-B. how we know how many data we have to select to detainment the percentage.

[Ezra Halleck]

For 3.6.6:
1. find the interval. From the data, you find the mean and standard deviation; the empirical rule says the interval for 95%, is from the mean minus 2 standard deviations to the mean plus 2 standard deviations.

2. see which data lie within the interval, then count them (if you have your data sorted, you can take the row index for your last data point, subtract the row index of the first data point and add 1). Finally, divide the count by the total number of data points. To convert to display as percentage, you click on the % icon on the home tab.

3.6.8 is essentially asking you to do the same thing.

[Ezra Halleck]

could you tell me how to do the question 3.6.10. e and f?

The empirical rule would say 68% of the data will lie within one standard deviation. To get the interval, you would add and subtract just one standard deviation from the mean. Once you have the interval, look at the discussion above for 3.6.6 to see how you get the percentage.