Probability of having a tire that lasts more

Question

Q1. The grades of 20 students are listed below. Use the stem & leaf to determine the shape of the distribution. Choose the best answer.

4 | 4
5 | 6 8
6 | 5 7 9
7 | 1 5 7 8 8 9
8 | 3 4 5 7 8 8 9
9 | 7

• The data is symmetric
• The data is skewed to the right
• The data is skewed to the left
• The data is bimodal

 

Q2. A researcher is considering using 90% confidence interval for his research project instead of 95%. What happens to the required sample size if the confidence level is decreased from 95% to 90% and the same error margin is allowed in each case?

• The sample size remains unchanged
• The sample size needs to increase
• The sample size needs to decrease
• Not enough information is provided to draw a conclusion regarding the sample size in this case.

Q3. Horse race time is found to be normally distributed with a mean value of 18 minutes and a standard deviation of 4 minutes. Horses whose race time is in the top 6% will not be eligible to participate in a second round. What is the lowers race time that makes a horse losses his eligibility to participate in a second round?

• 26.6
• 11.8
• 24.2
• 20.3

Q4. A class containing 25 students 12 of them are females. In how many ways can we select a group of 6 male students?

• 1716
• 665280
• 1235520
• 924

Q4. Research shows that the life time of Everlast automobile tires is normally distributed with a mean value of 65,000 miles and a standard deviation of 6,500 miles. What is the probability of having a tire that lasts more than 75,000 miles?

• 0.0618
• 1.54
• 0.9382
• 0.0606