Cam Barley

Greenhorn

Posts: 3

posted 6 years ago

Hey guys I have a quick question on my hw, I have found everything needed except the "unusual scores". this is the direction given:

Determine which of the grades, if any, are "unusual" in the sense that their corresponding z-score is < -2.0 or > +2.0. A z-score is computed as:

I know what the x bar and the s is, but I am unsure of what the first x is pertaining to. Can anyone give me a few tips?

Thanks

Determine which of the grades, if any, are "unusual" in the sense that their corresponding z-score is < -2.0 or > +2.0. A z-score is computed as:

I know what the x bar and the s is, but I am unsure of what the first x is pertaining to. Can anyone give me a few tips?

Thanks

Campbell Ritchie

Marshal

Posts: 56578

172

posted 6 years ago

. . . and welcome to the Ranch

I would presume

I would presume

*s*means standard deviation, in which case you are assuming the marks are normally distributed, and you should really be given*σ*as its symbol
Matthew Brown

Bartender

Posts: 4568

9

posted 6 years ago

Actually, looking at the formulas used, I think he does mean

Campbell Ritchie wrote:I would presumesmeans standard deviation, in which case you are assuming the marks are normally distributed, and you should really be givenσas its symbol

Actually, looking at the formulas used, I think he does mean

*s*. The

`stdDev`function is dividing by

*N - 1*, which means it's the sample standard deviation, rather than the standard deviation. And

*s*is the conventional notation for that.

Cam Barley

Greenhorn

Posts: 3

posted 6 years ago

thanks for all the quick replies Yes it is the std dev for the sample grades. I was unsure how to write the array for the unusual scores, I didn't know if it should have a loop for the grades to see if any of them are unusual, anyone have a tip?

Thanks

Matthew Brown wrote:Campbell Ritchie wrote:I would presumesmeans standard deviation, in which case you are assuming the marks are normally distributed, and you should really be givenσas its symbol

Actually, looking at the formulas used, I think he does means. ThestdDevfunction is dividing byN - 1, which means it's the sample standard deviation, rather than the standard deviation. Andsis the conventional notation for that.

thanks for all the quick replies Yes it is the std dev for the sample grades. I was unsure how to write the array for the unusual scores, I didn't know if it should have a loop for the grades to see if any of them are unusual, anyone have a tip?

Thanks

Matthew Brown

Bartender

Posts: 4568

9