Question

What are the mean, variance, and standard deviation of these values? Round to the nearest tenth.

(PICTURE BELOW)

Answer 1

@Phi , @amistre64

Answer 2

the sum of the xs divided by how many xs there are is the mean: \(\bar x\)

Answer 3

variance is similar, but you add up the last column and divide by how many there is

Answer 4

or for a shortcut

x - mean = n

x+n = mean ..... is constant

Answer 5

So what do i do

Answer 6

err, x-n = mean

notice the second column is x-mean, and gives some value "n"

x - mean = n, instead of adding up the first column and dividing off the number of rows ... just work the first entry for the mean.

x - n = mean

Answer 7

and variance is just the average of the last column

Answer 8

Okay one second

Answer 9

Do i add all of those like i did last problem ?

Answer 10

you can if you want to

Answer 11

and i recall that x bar is a sample mean ... so variance here will be slightly different

mean is still the same process tho

Answer 12

Yeah i still cant find my answer

Answer 13

and i cant see where your error is ....

Answer 14

My mean is 47.6

Answer 15

correct, mean is 47.6

Answer 16

whats my varice and SD ?

Answer 17

variance is 31 ?

Answer 18

the last column lists all the values from (x-mean)^2

so we just need to add up that column, and divide ..... except you have to divide by one less since its a sample

Answer 19

when i divide the sum by 4, i get 77.7 for variance

Answer 20

i got 31 as my variance

Answer 21

because i did 29.2+11.6+.6+0.2+2+112.4 = 155.4/5=31 for my variance

Answer 22

now i need to find my SD but dont know how to do that ?

Answer 23

sum of the last column is 155.4

so i must have added wrong, 155.4/4 = 38.85 for variance

and as before, sd = sqrt(var)

Answer 24

My SD is either 5.6 or 936.5

Answer 25

i dont have 38.85 as a variance on my answer choice

Answer 26

is the chart something that gave you? or is it something you created?

Answer 27

the chart was given

Answer 28

\[VAR_{pop}=\frac{sum(x-\mu)^2}{N}\]
\[VAR_{sample}=\frac{sum(x-\bar x)^2}{N-1}\]

Answer 29

they give you the \((x-\bar x)^2\) values to add up .... so divide that sum by 5-1

Answer 30

if you forgo their values and find your own, you get a sum of 155.2, divided by 4 gives a varaince of 38.8

Answer 31

This is my answer choice

Answer 32

then your choices are wrong.

make sure you have the correct question with the appropriate choices ... to be sure

Answer 33

i cant change my choices

Answer 34

What would my correct aswer be so i can tell my teacher ?

Answer 35

\[mean=\frac{5.4+3.4+0.4+1.4-10.6}{5}=\frac{\sum x}{5}\]
\[var=\frac{29.2+11.6+0.2+2+112.4}{5-1}=\frac{\sum(x-\bar x)^2}{4}\]
\[sd=\sqrt{(var)}\]

Answer 36

mean: 47.6
var: 38.85
sd: sqrt(38.85)

Answer 37

lol, i added the wrong column for mean :)

Answer 38

yeah see that isnt of my answer choice

Answer 39

\[mean=\frac{53+51+48+49-37}{5}=\frac{\sum x}{5}\]

Answer 40

mean: 47.6
var: 38.85
sd: sqrt(38.85) <-- whats my original answer ?

Answer 41

im not going to find a sqrt for you ... im just showing you how to find it.

Answer 42

6^2 = 36
7^2 = 49

so the sd is someplace betwee 6 and 7

Answer 43

if you just want to find the "correct" option. square the sd and see if it amounts to the var the provide

Answer 44

I'm still confused

Answer 45

sd^2 = variance

which option is the "most" correct?

mean = 47.6
var = sd^2
sd = sd

Answer 46

if they dont have the correct option, then you either choose none of them, or the "most correct" option

Answer 47

and id still bring it to your teachers attention

Answer 48

Can we skip this question ?

Answer 49

maybe, im not sure what your program allows you to do