// Numbas version: exam_results_page_options {"name": "Two Sample Hypothesis Test ( class test)", "metadata": {"description": "", "licence": "None specified"}, "duration": 0, "percentPass": 0, "showQuestionGroupNames": false, "showstudentname": true, "question_groups": [{"name": "Group", "pickingStrategy": "all-ordered", "pickQuestions": 1, "questions": [{"name": "Two Sample Hypothesis Test", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Shihan Miah", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/4456/"}], "tags": [], "metadata": {"description": "", "licence": "All rights reserved"}, "statement": "

A survey of passengers travelling from airports in London showed that passengers disliked waiting at security control. Two airports in London decide to investigate the issue.

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Heathrow Airport asked a random sample of 16 passengers to record how long they waited at security control. The mean waiting time for the sample was 31 minutes with a standard deviation of 7 minutes.

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London City Airport asked a random sample of 10 passengers to record the same information. The mean waiting time for the sample was 26 minutes with a standard deviation of 8 minutes.

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Assume that the waiting times for all passengers are normally distributed. Use a two sample t-test with a 5% significance level to determine if there is a    difference in waiting times at Heathrow Airport and London City Airport. 

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Fill the by writing appripriate words

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The null hypothesis is

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There is no difference between the wait times at Heathrow and City airports

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There is difference between the wait times at Heathrow and City airports

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The alternative hypothesis is: 

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There is no difference between the wait times at Heathrow and City airports

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There is  difference between the wait times at Heathrow and City airports

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Write down the number of degrees of freedom

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Write down the critical value to 2 decimal places at 5% significane level.

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Calculate the pooled sample standard deviation Sp to 2 decimal places.

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Calculate the test statistics to 2 decimal places.

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What is the conclusion?

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    \n
  1. The times taken for ten men to perform a task were measured. After training, designed to reduce the time, the men were tested again. The times in seconds were found and were as follows:
  2. \n
\n

 

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
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Man

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A

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B

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C

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D

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E

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F

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G

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H

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I

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J

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Time before

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27

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45

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51

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33

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49

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22

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23

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35

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41

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25

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Time after

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\n

22

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\n

37

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\n

45

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26

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44

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20

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16

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35

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\n

42

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\n

23

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\n

 

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Report on the effectiveness of the training as shown by this experiment. (Hint: this is a paired sample test, and as the sample is small we need to use a t test)

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Which one is the correct null hypothesis?

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 H0: there are no difference between the training time

", " H0: there are difference between the training time", " H0:  Training time is more before the training than after the training ", "H0:  Training time is less before the training than after the training "], "matrix": ["1", 0, 0, 0], "distractors": ["", "", "", ""]}, {"type": "1_n_2", "useCustomName": false, "customName": "", "marks": 0, "showCorrectAnswer": true, "showFeedbackIcon": true, "scripts": {}, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "adaptiveMarkingPenalty": 0, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "prompt": "

Which one is the correct alternative hypothesis?

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What is the critical  value at 5% significance level (3d.p.)

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Calculate the test statistics ( 2d.p.)

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Which one is the correct decesion?

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What is the conclusion

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The management in a large chain of shops aims to reduce the level of absenteeism among its staff. The management looks at two locations, a city centre shop in Manchester and a shop in Edinburgh.

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The company take a sample of 8 employee records in Manchester and record how many days each employee has been absent over the previous year. They find that the sample mean is 7 days with a sample standard deviation of 1.2

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They take a sample of 10 employees in Edinburgh and find that the sample mean is 6.2 with a sample standard deviation of 1.8. Carry out a two-sample t-test at a 5% significance level to determine if there is a difference in absenteeism between the two locations

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What is the null hypothesis?

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There is no difference between the stores.

", "

There is difference between the stores

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What is the alternative hypothesis?

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There is no difference between the stores

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There is difference between the stores

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Calculate pooled sampled standard deviation to 2 decimal places.

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Calculate test statistics to 2 decimal places.

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What is the number of degrees of freedom?

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Write down the critical value.

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What is the decision?

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