ShmoopTube

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And here's your shmoop du jour brought to you by pop quizzes the only [Boy blindfolded testing fizzy drinks]

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real way to test whether someone knows their coke from their pepsi alright quiz

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scores this quarter we're kind of low and your teacher decides to add five

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points to everyone's individual quiz grades how does this change the mean,

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standard deviation and interquartile range for the classes quiz scores. Huh,

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and here the potential answers....Okay this is a three-in-one deal pretty nice [Jacobs 3-in-1 coffee packet]

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when opening a peanut but not nearly as exciting when in the form of a math

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problem anyway let's just divide and conquer the first thing we need to [A knight wielding a sword]

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figure out is how the mean will be affected if everyone score gets five

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points tacked on to it plus reminder the mean is the same as the average so now

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we're just adding five points to a score or two well the average would definitely [teacher marking papers]

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be affected. But since every student is getting five bonus points across the

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board the mean goes up by 5 too. Although if you ask us it's not much of a bonus if [Boy in a suit throwing cash into the air]

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everyone gets one we don't want to raise, if everyone gets a raise like maybe

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we're too competitive for our own good so yeah imagine three people get scores of one

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two and three the mean of those scores is 1 + 2 + 3 divided by 3 or 2.. Add 5 to

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each of those scores and we get six seven eight the mean of those scores is

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six plus seven plus 8 divided by 3 or seven! exactly five higher alright well now that we've

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confirmed that tid bit of information well looks like we can kick answers D

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and E to the curb we're asked next about that standard deviation but before we [magnifying glass inspecting the question]

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start whipping out a formula or two let's think about this for a skinny

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minute the standard deviation is about how spread out the data are from each [example of a standard deviation formula]

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other well since each score is being affected in exactly the same way plus [teacher throws number into the air]

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five to each the scores aren't any further apart from each other than

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before so the standard deviation will stay the same kind of likes Beyonce [Two beyonces wearing sparkling dresses]

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seriously she hasn't changed in 15 years what is her secret? Now the only one of

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our three remaining choices that shows a standard

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deviation remaining the same is answer C so it looks like that's our horse but [A horse sniggering]

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let's double check the interquartile range too just to be sure. Well to find

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the interquartile range we have to subtract the value of Q 1 the first

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quartile from q3 the third quartile well since both of these scores will have had [Q1 substracted from Q3 value]

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five points added to them we're going to subtract five from five and those new

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points are going to cancel out completely meaning the interquartile

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range won't change a lick either which is still in line with option C and [Option C ticked green]

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that's going to be our answer whoa, we've got another three in one who exactly his

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growing these mutant peanuts [Man with 3 heads growing peanuts]

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