A comparison of the means of two groups (4).

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Christian Lawson-Perfect

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8 years, 9 months ago

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Christian Lawson-Perfect 8 years, 9 months ago

Gave some feedback: Ready to use

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Keith McGuinness 9 years, 8 months ago

Created this as a copy of A comparison of the means of two groups (3)..

Name	Status	Author	Last Modified
Paired t-test after treatment.	Ready to use	Bill Foster	01/06/2016 09:47
Christian's copy of Paired t-test after treatment.	Ready to use	Christian Lawson-Perfect	01/06/2016 10:06
A comparison of the means of two groups (1).	Ready to use	Keith McGuinness	01/06/2016 09:47
A comparison of the means of two groups (2).	Ready to use	Keith McGuinness	01/06/2016 09:47
Testing an hypothesis about the mean of a group (1).	Ready to use	Keith McGuinness	01/06/2016 09:47
Testing an hypothesis about the mean of a group (2).	Ready to use	Keith McGuinness	01/06/2016 09:47
Summary statistics (1).	Ready to use	Keith McGuinness	01/06/2016 09:47
A comparison of the means of two groups (3).	Ready to use	Keith McGuinness	01/06/2016 09:47
A comparison of the means of two groups (4).	Ready to use	Keith McGuinness	01/06/2016 09:47
A comparison of the means of three groups (1).	Ready to use	Keith McGuinness	01/06/2016 09:47
A comparison of the means of three groups (2).	Ready to use	Keith McGuinness	01/06/2016 09:47
A comparison of the means of four groups (1).	Ready to use	Keith McGuinness	01/06/2016 09:47
Simon's copy of Paired t-test after treatment.	draft	Simon Thomas	05/06/2019 14:44

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Question statement

A study is done looking at two drug treatments for use in heart transplants: (1) sodium salicylate; and (2) sodium salicylte and azathioprine. The trial is done using rats. The variable is survival time. The data is in the table below:

{object}	A	B	C	D	E	F
SS alone	$\var{group1[0]}$	$\var{group1[1]}$	$\var{group1[2]}$	$\var{group1[3]}$	$\var{group1[4]}$	$\var{group1[5]}$
SS + AZ	$\var{group2[0]}$	$\var{group2[1]}$	$\var{group2[2]}$	$\var{group2[3]}$	$\var{group2[4]}$	$\var{group2[5]}$

Is there a difference between average survival in the two groups?

In other words, test the following null hypothesis:

H0: mean survival SS = mean survival SS+AZ.

Note: Based on an exercise in Milton, JS (1980) Statistical methods in the biological and health sciences. McGraw-Hill.

Give any introductory information the student needs.

			Name	Type	Generated Value

combvar	number	22.8333333333
group1	list	[ 64, 62, 59, 60, 61, 73 ]
group2	list	[ 47, 49, 47, 50, 46, 58 ]
mean1	number	63.1666666667
mean2	number	49.5
mu1	integer	67
mu2	integer	56
object	string	Rat
objects	string	rats
outcome	integer	1
sec	number	2.7588242262
sig1	integer	10
sig2	integer	10
t95	number	2.228
thisn	integer	6
var1	number	26.1666666667
var2	number	19.5
tcalc	number	4.9538011653
df	integer	10
slip	number	0.025

Automatically regenerate variables?

Name

Data type

Value

xxxxxxxxxx
 
(var1*(thisn-1)+var2*(thisn-1))/(2*thisn-2)

JME function reference

Description

Describe what this variable represents, and list any assumptions made about its value.

Can an exam override the value of this variable?

Generated value: `number`

22.8333333333

← Depends on:

thisn
var1
var2

→ Used by:

Advice
"Unnamed part" → "Gap 4." - Minimum accepted value
"Unnamed part" → "Gap 4." - Maximum accepted value

Parts

Gap-fill
1. Gap Gap 0. Number entry
  Add
2. Gap Gap 1. Number entry
  Add
3. Gap Gap 2. Number entry
  Add
4. Gap Gap 3. Number entry
  Add
5. Gap Gap 4. Number entry
  Add
6. Gap Gap 5. Number entry
  Add
7. Gap Gap 6. Number entry
  Add
8. Gap Gap 7. Number entry
  Add
9. Gap Gap 8. Number entry
  Add

Gap-fill

Ask the student a question, and give any hints about how they should answer this part.

Summary statistics

Calculate means and variances for both groups: variance ($s^2$) is just the standard deviation ($s$ or $sd$) squared.

Note: All values, except df and outcome, should be given to 2 decimal places.

Mean 1 = Gap 0.; Mean 2 = Gap 1.

Variance 1 = Gap 2.; Variance 2 = Gap 3.

n1 = 6; n2 = 6

Combined standard error

First, calculate the combined variance:

Combined variance = Gap 4.

Second, calculate the combined standard error:

Combined SE = Gap 5.

t-calc and df

$t=\frac{Mean_1 - Mean_2}{SE_c}$

$df = (n1+n2-2) $

t-calc = Gap 6.

df = Gap 7.

Outcome

Compare t-calc to the table value, t-table, which is 2.228, and reject the null if t-calc > t-table.

Outcome = Gap 8. (Enter 0 if the null is accepted; 1 if it is rejected.)

Advice

Summary statistics

Calculate means and variances for both groups: variance ($s^2$) is just the standard deviation ($s$ or $sd$) squared.

Mean 1 = {mean1}; Mean 2 = {mean2}

Variance 1 = {var1}; Variance 2 = {var2}

n1 = 6; n2 = 6

Combined standard error

First, calculate the combined variance:

Combined variance = {combvar}

Second, calculate the combined standard error:

Combined SE = {sec}

t-calc and df

$t=\frac{Mean_1 - Mean_2}{SE_c}$

$df = (n1+n2-2) $

t-calc = {tcalc}

df = {df}

Outcome

Compare t-calc to the table value, t-table, which is 2.228, and reject the null if t-calc > t-table.

Outcome = {outcome} (Enter 0 if the null is accepted; 1 if it is rejected.)

Give a worked solution to the whole question.

Use this tab to check that this question works as expected.

There was an error which means the tests can't run:

Part	Test	Passed?
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A comparison of the means of two groups (4).

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Taxonomy: mathcentre

Taxonomy: Kind of activity

Taxonomy: Context

Contributors

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Checkpoint description

Christian Lawson-Perfect 8 years, 9 months ago

Keith McGuinness 9 years, 8 months ago

Error in variable testing condition

Error

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Generated value: `number`

Parts

Gap-fill

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Error

A comparison of the means of two groups (4).

Metadata

Taxonomy: mathcentre

Taxonomy: Kind of activity

Taxonomy: Context

Contributors

Feedback

History

Comment

Checkpoint description

Christian Lawson-Perfect 8 years, 9 months ago

Keith McGuinness 9 years, 8 months ago

Error in variable testing condition

Error

Warning

Generated value: number

Parts

Gap-fill

Generated value: `number`