RISKY SHIFT: LAB REPORT WRITE-UP

RISKY SHIFT:

LAB REPORT WRITE-UP

Week 7 Practical

WEEK 1

WEEK 2

WEEK 3

WEEK 4

WEEK 5

WEEK 6

WEEK 7

WEEK 8

WEEK 9

WEEK 10

LECTURE PRACTICAL

NONPARAMETRICS 1 1ST PRACTICAL

NONPARAMETRICS 2 1ST ANALYSIS

SAMPLING DISTRIBUTIONS

1ST ANALYSIS + PROBLEMS 1

HYPOTHESIS TESTING

2ND PRACTICAL

RELATED T-TEST

2ND ANALYSIS + SOLUTIONS 1

INDEPENDENT T-TEST

INDEPENDENT ANOVA

DEPENDENT ANOVA

2ND ANALYSIS + PROBLEMS 2

3RD PRACTICAL

3RD ANALYSIS + SOLUTIONS 2

3RD ANALYSIS + PROBLEMS 3

NO LECTURE NO PRACTICAL

WEEK 7 PRACTICALRISKY SHIFT

Tackle an additional problem sheet which should help you understand the principles behind non-parametric tests more fully.

Learn to calculate the Wilcoxon test by hand.

Understand the way in which the practical reports will be marked and what you have to do to do well!

BY THE END OF THE SESSION, YOU SHOULD BE ABLE TO:

Clarify any additional problems that you may have regarding this lab report with your friendly neighbourhood demonstrators.

LEARNING OUTCOMESRISKY SHIFT

PRACTICAL WRITE-UP

INTRODUCTION

METHOD

RESULTS

DISCUSSION

ABSTRACT

TITLE

REFERENCES

APPENDICIES

212

20

20

20

20

6

0

IV and DV included, precise, concise

Maximum 150 words, summary of all sections

Clear structure leading to experimental rationale

Evidence of extra reading, beyond the handouts

Sufficient information to replicate the study

Participants, materials, design, procedure

Clear and logical descriptive and inferential stats

Well designed figures related to the findings

Summary of main results, relating to introduction

Evaluation of study, suggestions for future

APA formatted, consistent with references in text

Handouts, SPSS printouts, workings out…

RISKY SHIFT

WILCOXON BY HANDRISKY SHIFT

DOWNLOAD AND SAVE THE FILE ‘WILCOXONBYHAND’

First, you should be able to complete the smaller exercise on the Wilcoxonbyhand document, and check

your workings using ‘wilcoxonbyhand_done’

There is an addition exercise which provides you with the steps to carry out a Wilcoxon by hand on the Risky

Shift data using Excel. Taking a look at this exercise should improve your Excel skills if nothing else.

DO NOT PANIC ABOUT GETTING THROUGH BOTH EXERCISES.

FOCUS ON UNDERSTANDING HOW TO DO WILCOXON BY HAND.

DOWNLOAD AND SAVE THE FILE ‘WILCOXONBYHAND_DONE’


Wilcoxon testRATINGS + WITHIN Ss + 2 GROUPS

NON-PARAMETRIC TESTS (1)

GROUP 1: Radiohead

GROUP 2: LCD Soundsystem

03, 05, 04, 04, 07, 10, 04, 05, 05

13, 17, 12, 17, 06, 10, 16, 17, 19

(a) Find the difference between score pair and retain the sign

(b) Rank the differences ignoring their sign. Ignore zero differences

(c) Ranking criteria as in Mann-Whitney

WILCOXON TEST

03, 05, 04, 04, 07, 10, 04, 05, 05

13, 17, 12, 17, 06, 10, 16, 17, 19

10, 12, 08, 13, -01, 00, 12, 12, 14

(-)01, 08, 10, 12, 12, 12, 13, 14

(-)01, 02, 03, 04, 05, 06, 07, 08

(-)01, 02, 03, 05, 05, 05, 07, 08

NON-PARAMETRIC TESTS (1) WILCOXON TEST

GROUP 1: Radiohead

GROUP 2: LCD Soundsystem

03, 05, 04, 04, 07, 10, 04, 05, 05

13, 17, 12, 17, 06, 10, 16, 17, 19

(-)01, 02, 03, 05, 05, 05, 07, 08

(d) Add positive and negative signed ranked independently

(e) Note the smaller sum of ranks (W)

(f) Note the number of non-0 differences (N)

Negative Ranks = 01 Positive Ranks = 35

W = 1

N = 8

Here’s a reminder of how to do the Wilcoxon ranking from the lecture…

Follow the sheet to complete a Wilcoxon for the small data set.

Tackle an additional problem sheet which should help you more fully understand the principles behind non-parametric tests.

Learn to calculate the Wilcoxon test by hand.

Understand the way in which the practical reports will be marked and what you have to do to do well!

BY THE END OF THE SESSION, YOU SHOULD BE ABLE TO:

Clarify any additional problems that you may have regarding this lab report with your friendly neighbourhood demonstrators.

LEARNING OUTCOMESRISKY SHIFT

YOUR CHOICE

YOU HAVE THE REST OF THE SESSION TO FOCUS ON WHAT YOU THINK YOU NEED TO IMPROVE YOUR UNDERSTANDING

LAB REPORT TESTS BY HAND NONPARAMETRICS

Try working through the second Wilcoxon

analysis using the ‘riskyinexcel’ workbook and

compare your hand results with the

results you obtained from SPSS.

The brave could also try a Friedman’s test

by hand using Graham’s guide.

Make sure you are happy with your

interpretation of the SPSS output in

relation to the three experimental

hypotheses ,and make sure you know what

needs to go into your lab report to get the

best marks.

Download ‘problem5’ and start to work

through the questions related to the

forthcoming related t-test (as well as some problems relating to

correlation and regression).

RISKY SHIFT

DOWNLOAD AND SAVE THE FILE ‘RISKYINEXCEL’


There’s an awful lot of data here, so it’s probably best to focus on one of the hypotheses and take it slowly.

Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment?


At the bottom of the sheet (and the

separate Word file), there are instructions on how to calculate

Wilcoxon using Excel.

DOWNLOAD AND SAVE THE FILE ‘WILCOXONBYHAND’




1) CALCULATE THE DIFFERENCE BETWEEN D AND C SCORES IN (H) AND RETAIN THE SIGN. = CELLab- CELLcd




2) CALCULATE THE ABSOLUTE DIFFERENCE FOR (H) IN (J) =ABS (CELL)




3) COPY AND PASTE ID AND SCORE VALUES FROM COLUMN I AND J INTO COLUMN K AND L EDIT > COPY




4) SORT COLUMNS K AND L BY COLUMN L (RANKED DIFFERENCES) DATA > SORT > SORT BY

We are doing this as an easy way to rank order

the data, but we also need to keep track of whether

these differences are positive or negative in the

final analysis. Hence, each individual difference keeps its unique id code.




5) BEGINNING WITH THE FIRST NON-ZERO DIFFERENCE IN COLUMN N ASSIGN RANK SCORES STARTING AT 1




6) SCORES THAT SHARE THE SAME NON-ZERO DIFFERENCE MUST SHARE AVERAGE RANK IN COLUMN P

The first 11 numbers all share a difference of 0.4,

so they are all assigned the rank

value of 6 (1+2+3+4+5+6+7+8

+9+10+11/11 = 6)




7) TAKE THE SORTED ID VALUES FROM COLUMN K AND PASTE INTO COLUMN O

8) NOTE THAT IN COLUMN S, THE ORIGINAL SIGNED DIFFERENCES ARE ALREADY THERE




9) SORT COLUMNS O AND P BY COLUMN O (ASCENDING) DATA > SORT > SORT BY




10) COPY AND PASTE VALUES FROM COLUMN P OVER TO COLUMN U DATA > SORT > SORT BY




11) REINSTATE NEGATIVE VALUES WHERE APPROPRIATE




12) SORT COLUMN U (ASCENDING)




Congratulations! You now have everything you need to finish the test!

SUM NEGATIVE SUM POSITIVE

No. NEGATIVE No. POSITIVE TOTAL OBSERVATIONS

828 33

37 4 41

Ranks

37a 22.38 828.00

4b 8.25 33.00

7c

48

Negative Ranks

Positive Ranks

Ties

Total

grp mean1_5 -pre mean1_5

N Mean Rank Sum of Ranks

grp mean1_5 < pre mean1_5a.

grp mean1_5 > pre mean1_5b.

grp mean1_5 = pre mean1_5c.

NOTE: This is exactly the same data

produced by SPSS!




Congratulations! You now have everything you need to finish the test!

SUM NEGATIVE SUM POSITIVE

No. NEGATIVE No. POSITIVE TOTAL OBSERVATIONS

828 33

37 4 41

We use the smaller of the sums (33) as our observed W. We use the total number of non-zero observations (41) as our df.

Look up the critical value of W, taking into account N. If our obtained W is smaller than the critical value of W, we reject the null

hypothesis and conclude that two groups do differ significantly.




Obtained W = 33

Critical W = 89

N = 41

Obtained W < Critical W

There is a statistically significant difference

between the two groups

Table only goes up to N = 25 but this is good enough (the critical value would be much bigger than 89 for an N = 41)

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