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s1 help

1) peice of data from 9 people. data mean was 35.5 but one of the 9 people gave a value of 42 instead of 32

a) write down effect - obv the mean will increase since 42 is > mean

b) calculate new mean

so i thought b) was 32x8 + 42 divide by 9 but its not. confused!

Reply 1

RDKGames

Study Forum Helper

Original post by seconda1

We have

35.5 = \dfrac{T_8 + 42}{9}

where

T_8

is the total data from 8 people and the 42 is the leftover data from the ninth person who got it wrong.

You want to use this equation to determine the value of

\dfrac{T_8+32}{9}

Reply 2

username3492572

Original post by RDKGames

We have

35.5 = \dfrac{T_8 + 42}{9}

where

T_8

is the total data from 8 people and the 42 is the leftover data from the ninth person who got it wrong.

You want to use this equation to determine the value of

\dfrac{T_8+32}{9}

im confused was is t?

Reply 3

RDKGames

Study Forum Helper

Original post by seconda1

im confused was is t?

I've just explained it. It's a variable to denote the total of the other 8 people.

Like y'know, when calculating the mean of like 4 people you'd do something like

\dfrac{1+2+3+4}{4}

but you can freely take the sum of the first three numbers 1+2+3 = 6 and just rewrite the mean as

\dfrac{6+4}{4}

. Same idea here, except we do not know the mean of the 8 people so we just denote it by

T_8

Reply 4

username3492572

Original post by RDKGames

I've just explained it. It's a variable to denote the total of the other 8 people.

Like y'know, when calculating the mean of like 4 people you'd do something like

\dfrac{1+2+3+4}{4}

but you can freely take the sum of the first three numbers 1+2+3 = 6 and just rewrite the mean as

\dfrac{6+4}{4}

. Same idea here, except we do not know the mean of the 8 people so we just denote it by

T_8

still confused

the mark scheme says 9x35.5 -10 / 9
why is it -10?

Reply 5

RDKGames

Study Forum Helper

Original post by seconda1

still confused

the mark scheme says 9x35.5 -10 / 9
why is it -10?

Because if you take the eq. I said and proceed to say

Unparseable latex formula:

\begin{aligned} 35.5 & = \frac{T_8 + 42}{9} \\ & = \frac{T_8 + 32 + 10}{9} \\ & = \frac{T_8+32}{9} + \dfrac{10}{9}

then just subtract 10/9 from both sides to get the answer they're looking for.

(edited 6 years ago)

Reply 6

username3492572

Original post by RDKGames

Because if you take the eq. I said and proceed to say

Unparseable latex formula:

\begin{aligned} 35.5 & = \frac{T_8 + 42}{9} \\ & = \frac{T_8 + 32 + 10}{9} \\ & = \frac{T_8+32}{9} + \dfrac{10}{9}

then just subtract 10/9 from both sides to get the answer they're looking for.

so the data was said to have found a mean of 35.5 and then it says one person out of the 9 had the 42 instead of 32 so cant you work out the mean of 8 people because its 32x8/8?

cant seem to get my head around this

Reply 7

RDKGames

Study Forum Helper

Original post by seconda1

Why would you want the mean of 8 people? Also no, the mean of the 8 people is given by

\dfrac{T_8}{8} = \dfrac{9\cdot 35.5-42}{8}

instead.

Anyway, I don't know how else to explain it so I'll leave it to someone else. All I can do is repeat myself by saying that each person has data values of