Question: Units of Standard Deviation

Rate this video: 
5

Comment on Units of Standard Deviation

When the question asks for the numbers that are more than half the unit of standard deviation, would not it be the numbers that are greater than 6.9 ? Why do choose the numbers that fall below 6.9? Please reply. Thanks.
greenlight-admin's picture

The question is asking us to identify all values that are more than 0.5 units of standard deviation BELOW the mean.

0.5 units of standard deviation BELOW the mean = 9 - (0.5)(4.2) = 6.9

0.6 units of standard deviation BELOW the mean = 9 - (0.6)(4.2) = 6.48. This means that 6.48 is more than 0.5 units of standard deviation BELOW the mean

Likewise, 0.7 units of standard deviation BELOW the mean = 9 - (0.7)(4.2) = 6.06. This means that 6.06 is more than 0.5 units of standard deviation BELOW the mean

Does that help?

So, What happen with numbers 14 and 18 are? Why are they not included as part of the answer ? if they are numbers > 0.5 units of SD in the right side.
greenlight-admin's picture

The question does not ask us to identify values that are more than 0.5 units of SD AWAY from the mean. It asks us to identify values that are more than 0.5 units of SD BELOW (less than) the mean

Thanks so much. Probability, I didn't pay attention to the word "below". So, Everything is clear now.
dr3wamy's picture

im really amazed with ur videos and prompt replies ...thnx a lot.
greenlight-admin's picture

Glad to help!

Hi! Can you use a proportion for the units of SD. For example, 1 unit of SD/4.2 SD = 0.5 units of SD/x SD to get 2.1?
greenlight-admin's picture

Most definitely!

Great exercise!. At first I answered 6, but those are the number below the mean. The answer ask for the numbers 0.5 units of SD below of the mean.

how do you determine 6 as the answer by looking at
7.6 below , 12, mean 16.4 above.
greenlight-admin's picture

Tuttiam52 isn't saying that the correct answer is 6.

With "Units of Standard Deviation (SD)" questions, we often look at units of SD ABOVE the mean and units of SD BELOW the mean.

This question asks for 0.5 units of SD BELOW the mean.
So, we must SUBTRACT 2.1 from the 9 (the mean)

For more on this see: https://www.greenlighttestprep.com/module/gre-statistics/video/808

Add a comment

Have a question about this video?

Post your question in the Comment section below, and we’ll answer it as fast as humanly possible.

Change Playback Speed

You have the option of watching our videos at various speeds (25% faster, 50% faster, etc). To change the playback speed, click the settings icon on the right side of the video status bar.

Let us Know

Have a suggestion to make our course even better? Email us today!

Free “Question of the Day” emails!