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Assignment 6

1) The effect of alcohol on useful consciousness: Ten pilots performed tasks at asimulated altitude of 25,000 feet. Each pilot performed the tasks in a completelysober condition and, three days later, after drinking alcohol. The response

variable is the time in seconds of useful performance of the tasks for eachcondition. The longer a pilot spends on useful performance, the better. Theresearch hypothesis is that useful performance time decreases with alcohol use.The data are as follows:

Pilot No Alcohol Alcohol

1 261 185

2 565 375

3 900 310

4 630 240

5 280 215

6 365 4207 400 405

8 735 205

9 430 255

10 900 500

Graph these data. What are the null and alternative hypotheses? What is theappropriate statistical test and why? Do that test using SPSS and report theresults in APA format, including the effect size. Interpret the results in words.

Paired Samples Statistics

Mean N Std. Deviation Std. Error

Mean

Pair 1Noalcohol 546.6000 10 238.81197 75.51897

Alcohol 311.0000 10 108.03292 34.16301

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Paired Samples Test

Paired Differences t d

f

Sig.

(2-

tailed

)

Mean Std.

Deviation

Std.

Error

Mean

95% Confidence

Interval of the

DifferenceLower Upper

Pai

r 1

Noalcoho

l -

Alcohol

235.6000

0

227.4990

6

71.9415

2

72.8569

8

398.3430

2

3.27

59 .010

Null: There is no difference in performance when pilots are given alcohol, compared to when

they are flying sober.

Alternative: There is a decrease in performance when pilots are given alcohol, versus when they

fly sober.

Use a: One directional Paired t-test, because:

Were doing a within-subjects experimental design.

o Each participant has two pairs of scores.

Were making a one-directional hypothesis.

t(9) = 3.28, p = 0.005 (one-tailed), r^2 = .54

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Our experiment supports the idea that there is a significant decrease in performance when pilots

are given alcohol, versus when they fly sober. According to the effect size coefficient, a large

amount of the variance and magnitude on performance can be attributed to the treatment of

alcohol.

2) A researcher wanted to determine whether fear of spiders is specific to realspiders or whether pictures of spiders can evoke similar levels of anxiety.Twenty four subjects participated in the study. Twelve were asked to handle aspider and their anxiety level was measured. Twelve other subjects were shownpictures of a spider and their anxiety level was measured. Larger numbersrepresent greater anxiety. The results are shown below.

Picture of Spider Real Spider

30 40

35 35

45 50

40 55

50 65

35 55

55 50

25 35

30 30

45 50

40 6050 39

Graph these data. What are the null and alternative hypotheses? What is theappropriate statistical test and why? Do that test using SPSS and report theresults in APA format, including the effect size. Interpret the results in words.

Null: There is no difference on anxiety between participants given a picture of a spideror participants handling a real spider.

Alternative: There is a difference on anxiety between participants given a picture of aspider or participants handling a real spider.

Use a: Two-directional T-test of independent groups, because:

We have two different indepdent treatments, for a between-subjects experiment.

Groups observed indepdently.

Data seems normally distributed.

SPSS tells us the two groups are similarly varied.

Were not making a directional hypothesis.

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Group Statistics

GroupSpider N Mean Std. Deviation Std. Error

Mean

AnxietyLevel Picture of Spider 12 40.0000 9.29320 2.68272Real Spider Eeek 12 47.0000 11.02889 3.18377

t(22)= -1.681, p < .107 ( two-tailed ).

The significance level (2-tailed) was not less than 0.05 ( 0.107), meaning that theres nosignificant difference on anxiety on a participants who see a picture of a spider versusthose who handle a real spider. Theres no need to report an effect level, because thenull hypothesis was not disapproved.

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