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# S1 help Watch

1. I feel really stupid for needing help on this question but oh well.

http://www.ocr.org.uk/Images/65851-q...atistics-1.pdf

On question number 4, I don't understand how to do part 2 and also part 4; I got the answer to part 4 correct, but I guessed it. Can someone explain to my why it's decrease, increase then stay the same for the other two please.

For 4 part 2 I worked out that the median is 26th value so it's in the 31 to 35 class width but then I don't know what to do.
2. (Original post by Music99)
I feel really stupid for needing help on this question but oh well.

http://www.ocr.org.uk/Images/65851-q...atistics-1.pdf

On question number 4, I don't understand how to do part 2 and also part 4; I got the answer to part 4 correct, but I guessed it. Can someone explain to my why it's decrease, increase then stay the same for the other two please.

For 4 part 2 I worked out that the median is 26th value so it's in the 31 to 35 class width but then I don't know what to do.
The midpoint of the class is 33. Is the median before, or after the middle value of the class. i.e. there are 28 values, is it before the median of the class 31 to 35.
As for part iv)
The mean is reduced as one of the values is reduced - look at how you calculate the mean, it should make sense.
The sd increases because the lead time gets further away from the mean - the spread increases (this effect is greater than the effect of the reduced mean)
The person who came first changing does not affect the median - they are still first.
The IQR is unaffected as well as the person who came first does not lie between Q1 and Q3.

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Updated: April 3, 2013
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