Question

CAN SOMEONE PLEASE HELP?!!
Need help with the P-value of part e.
see attachment.

Answer 1

@jim_thompson5910 Can you help with this PRETTY PLEASE? :)

Answer 2

does it make any mention anywhere that the population variances are assumed to be equal?

Answer 3

you mean like normally distributed?

Answer 4

no i mean does it say anywhere that the two distributions are assumed to have equal variances?

Answer 5

no i'm not seeing that anywhere.

Answer 6

hmm

Answer 7

I'm getting the example so maybe that can help.

Answer 8

ok let me have a look at that please

Answer 9

ok it doesn't say it explicitly, but they're implying that the variances are not assumed to be equal

Answer 10

they should have stated this in the beginning because it drastically affects the answer

Answer 11

yah it's not the first time they've left an in portent piece of info out. That happens a lot.

Answer 12

anyways, it's a long drawn out process, so here we go...

Answer 13

We find the p value following these 3 steps


1) Find the standard error SE


2) use the SE to find the test statistic t


3) use the test statistic to find the p value (it's the area under the curve to the right of t)


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Standard Error (SE)(Assuming the population variances are NOT equal):



SE = sqrt( ((s1)^2)/(n1) + ((s2)^2)/(n2) )


SE = sqrt( ((9.5)^2)/(28) + ((11)^2)/(27) )


SE = sqrt( (90.25)/(28) + (121)/(27) )


SE = sqrt( 3.22321428571429 + 4.48148148148148 )


SE = sqrt( 7.70469576719577 )


SE = 2.77573337465899


The standard error is SE = 2.77573337465899


-------------------------------------------------------------------------


Test Statistic


t=(observed difference - expected difference)/(Standard Error)



t=((xbar1-xbar2)-(mu1-mu2))/(SE)



t=((71.9-69.1)-0)/(2.77573337465899)



t=(2.8)/(2.77573337465899)



t=1.00874241941339


t=1.0087


The test statistic is roughly t=1.0087


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Now find the area under the T distribution curve (df = 27 - 1 = 26) to the right of t=1.0087


We do this by using a table or a calculator. I'm going to use a calculator (this one: http://www.danielsoper.com/statcalc3/calc.aspx?id=41)


When you type in 26 for the degrees of freedom and 1.0087, you'll get 0.83879281 as the result. This is the area under the curve to the left of t = 1.0087, but we want it to the right, so we subtract it from 1 to get:


1 - 0.83879281


0.16120719


0.161


So the p value is 0.161

Answer 14

OOHH ok that actually made sense!

Answer 15

the p value is ____

the significance level is _____


Rule:

if the p value is less than the significance level, you reject Ho

if the p value is greater than or equal to the significance level, you fail to reject Ho

Answer 16

once you make your decision (to reject or fail to reject Ho) tell me what the conclusion is

Answer 17

so i don't reject it cause the p-value is greater then a=0.05 right?

Answer 18

good, you fail to reject Ho

so you have no choice but to "accept" Ho

Answer 19

what does this mean in terms of the final conclusion?

Answer 20

well i don't know if it's A or C.

Answer 21

what is the null hypothesis

Answer 22

I think it's C.

Answer 23

what is the null hypothesis

Answer 24

It's what i got for (e) B

Answer 25

I know, i want you to read it out for me

Answer 26

or write it out for me

Answer 27

lol fine. 1 sec.

Answer 28

you'll probably see the answer as you're writing it out

Answer 29

H0:Ufall=Uspring VS H1:Ufall>Uspring

Answer 30

ok so if we fail to reject Ho, or "accept" Ho

then we "accept" that Ufall=Uspring

Answer 31

this tells us that the means of the two classes (fall and spring) are not statistically different

Answer 32

so is there an improvement when it comes to the online component?

Answer 33

no?

Answer 34

you are correct, there is no statistical difference ---> no statistical improvement

Answer 35

so there's isn't sufficient evidence that the online homework is effective in raising final exam scores

Answer 36

if there was sufficient evidence that the online homework is effective in raising final exam scores, this would have to mean that

Ufall > Uspring

which would make you reject Ho

Answer 37

but since we didn't reject Ho, we don't have enough evidence to do so

Answer 38

YAY it says it's right!

Answer 39

yes that's good because it definitely is correct lol

Answer 40

then again, this system is a bit strange (ex: leaving out critical info), so who knows

Answer 41

is it the same thing for this?

Answer 42

yes, but this time you're finding the area to the left of t

Answer 43

UGH they can never make it simple can they? lol

Answer 44

unfortunately no

Answer 45

ok so i do SE = sqrt( ((s1)^2)/(n1) + ((s2)^2)/(n2) )
and t=((xbar1-xbar2)-(mu1-mu2))/(SE)?

Answer 46

correct

Answer 47

I got SE=3.446286454 & t=-3.191841464

Answer 48

getting the same for both

Answer 49

now use t to find the p value

Answer 50

what was the name of the calculator you used on here? http://www.danielsoper.com/statcalc3/default.aspx

Answer 51

http://www.danielsoper.com/statcalc3/calc.aspx?id=41

Answer 52

i got 0.00195883

Answer 53

so the P-value will be 0.002?

Answer 54

Got it!!

Answer 55

the p-value is less then a=0.02 so i reject it.

Answer 56

let me check

Answer 57

lol i already got it. it says it's right.

Answer 58

Do you have time for at least one more so i can hand this homework in with at least a 90%?

Answer 59

it's another P-value thing with a different kind data table.

Answer 60

same basic steps, but now you're going back to the right of t

Answer 61

how tho? there are more numbers so how do i start to solve it?

Answer 62

those values are used to find xbar and s (standard deviation)

but that's given above the data sets

Answer 63

so they did some of the work for you

Answer 64

oh i see the xbarA & B and the Sa & b. what do i do now?

Answer 65

those are the values you use to determine SE and t

Answer 66

like you did before

Answer 67

but i don't see a value for N1 or N2.

Answer 68

N1 is the number of numbers in the first set

N2 is the number of numbers in the second set

Answer 69

ooohh ok

Answer 70

SE=6.407703697 & t=0.2809118656

Answer 71

let me confirm

Answer 72

hmm I'm getting SE = 0.796031825159438

Answer 73

you got n1 = 30 and n2 = 30 right?

Answer 74

ok i'll try again. but yah i'm using n1 & n2=30

Answer 75

ok now t=2.261216126

Answer 76

so the p-value=0.016?

Answer 77

yep t=2.26121612617621

Answer 78

YAY!! it says it's right!

Answer 79

getting the same thing, nice work

Answer 80

THANK YOU!!!

Answer 81

yw