Statistics Problem Set

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PROBLEM SET NO. 2

PROBLEM SOLVING: Solve the following problems. Show all pertinent solutions.

1.A car battery dealer is trying to determine which of the brands of car battery he is selling has a longer life span. He conducted an investigation by interview his customers and was able to get the following results: Brand X Brand Y Mean life span 4.5 years 4.9 years Standard deviation 0.56 year 0.45 year Sample size 10 12

If you were the car dealer, could you conclude that brand Y is superior to Brand X? Use 5% level of significance.

2.A die was rolled 210 times. The results are shown below.

|Outcome |1 |2 |3 | |Bachelor’s Degree |10 |23 |7 | |Master’s Degree |16 |10 |8 | |Doctoral Degree |10 |6 |5 |

Based on the data, can we say that teaching efficiency is related to educational background? Use 5% level of significance.

5.The average typing speed of a good typist is said to be 60 words per minute. In a certain company, 45 applicants were given a typing test and the results showed a mean of 55 words per minute with a standard deviation of 10 minutes. Based on these results, can we say that the typing speed of the 45 applicants is below the average? Use α = 0.03.

6.A lot contains 20 electric bulbs, 5 of which are defective. In how many ways can 4 bulbs be taken for inspection such that: (a) no defective electric bulb is included? (b) 2 of the defective bulbs...
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