The scores of adults on a IQ test are approximately normal with mean 100 and standard deviation 15.

INSTRUCTIONS TO CANDIDATES

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EXAM PROBLEMS:

1) Following histogram shows result of a survey hold among a group of 88 smokers concerning the average number of cigarettes smoked per day

a. Describe shape, center and variability of the distribution

b. Which is the percentage of smokers consuming more than 25 cigarekes per day

c. How many smokers from this sample smoke less than 16 cigarettes daily?

2) Considering following data distribution, using Excel: 0,4,4,5,5,5,6,6,6,6,7,7,8,9

a) Calculate mean, median, and quartiles

b) Draw the boxplot

c) Is there any outlier? Why?

3) The scores of adults on a IQ test are approximately normal with mean 100 and standard deviation 15.

a. What proportion of adults have an IQ below 90?

b. What proportion of adulfs have an IQ above 120?

c. What proportion of adults have IQ between 90 mm and 11O mm?

4) A manager of an e-commerce company would like to determine average delivery time of the products. A sample of 25 customers is laken. 'the average delivery time in the sample was four days. Suppose the delivery times are normally distributed with a standard deviation of 1.2 days.”

a) Provide a 95 % confidence interval for the mean delivery time.

b) The manager claims that the average delivery time of their products does not exceed 3 days. Write the null and alternative hypothesis regarding to the claim of the manager.

c) Test the manager's claim

5) Sales of a car dealer during last year have been: January: 100 cars (Previous forecast 120) February: 120 (Previous forecast 130)

March: 140 (Previous forecast 200)

April: 110 (Previous forecast 90)

May: 175

June: 200

July: 250 August: 8B September: 120

October: 120:

November: 150

December: 130

Forecast the sales from May to August of present year using:

a) Na'ive approach

b) Moving averages

c) Exponential smoothing 

6) Create your own correlation

a. Invent two variables (can be a real example)

b. Define which one is dependent and which independent

G. Invent values

d. Graph a scatterplot using Excel

e. Graph the correlation line, find its equation and the index of correlation using Excel f Give your conclusions

 

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