Statistics - math problems

Number of problems found: 355

Suppose 4
Suppose that 14% of all steel shafts produced by a certain process are nonconforming but can be reworked (rather than having to be scrapped). Consider a random sample of 200 shafts, and let X denote the number among these that are nonconforming and can be
Rich retirement
Health care issues are receiving much attention in both academic and political arenas. A sociologist recently conducted a survey of citizens over 60 years of age whose net worth is too high to qualify for government health care but who have no private hea
Publishing company
Suppose you work for a publishing company and before launching a new magazine targeting fashion-oriented consumers, your boss wants to hold a meeting with perspective advertisers. Assume that annual expenditures on magazine ads in this genre are normally
A plumber
A plumber has the following lengths of PVC: 3.3 ft, 9.77 ft, 8.41 ft, 9.61 ft, 8 ft. What is his average length of PVC
Day trip
A group of tourists went on a day trip. For two hours they walked at a speed of 6 km/h, for another hour they climbed a steep hill at a speed of 2 km/h, spent an hour and a half at lunch, then in an hour they inspected the castle garden at a free step at
Range, mean, median
Ages of 7 employees in an office are given below 32, 42, 30, 32, 33, 23, 32 Find a) Range b) Mean c) Median
A frequency
A frequency table of grades has five classes (A, B, C, D, F) with frequencies of and 2,14,13,8 and 1 respectively. Using percentages, what are the relative frequencies of the five classes?
The average 3
The average of fraction is 7/10. One of the fractions is 2/3, the other fraction is?
Mortality tables
Mortality tables enable actuaries to obtain the probability that a person at any age will live a specified number of years. Insurance companies and others use such probabilities to determine life-insurance premiums, retirement pensions, and annuity paymen
Manufacturing company
A random sample of 8 manufacturing companies is selected from a population of manufacturing companies. The market values (in millions of rands) of these 8 manufacturing companies are: 17 65 117 206 172 181 221 94 What is the lowest and highest market valu
Binomial probability
What is the binominal probability that at least 4 of the 6 trials (n=6) are succeeded where φ = 0.50?
Language test
Your language test scores are 58, 68, 89 and 95. What is the lowest you can earn on the next test and still achieve an average of at least 79?
Level of significance
At a certain college it is estimated that 25% of the students have cars on campus. Does this seem to be a valid estimate if in random sample of 90 college students, 28 are found to have cars? Use a 0.05 level of significance.
A professor
A professor in a typing class found out that the average performance of an expert typist is 85 words per minute. A random sample of 16 students took the typing test and an average speed of 62 words per minute was obtained with a standard deviation of 8. C
Unemployment rate
Over the last 16 years, the country's unemployment rate has changed according to the following frequency table: years of unemployment: 2 5 2 3 3 1 unemploymen rate: 0.5 1 1.5 2 2.5 3 in % (percent). Determine the two-sided confidence interval for the vari
Chi square
A manufacturer of phone batteries claims that his batteries' lives are approximately normally distributed with a standard deviation equal to 0.9 years. If a random sample of 10 of these batteries has a standard deviation of 1.2 years. Do you think that th
Confidence Interval
The average grade of 50 students senior students in a statistics class is 85 with a standard deviation of 10.2 while a group of 60 senior students got an average of 80 with a standard deviation of 8.9, can the difference in the mean grade be attributed to
Performance comparing
A standardized test was administered to thousands of students with a mean score of 85 and a standard deviation of 8. A random sample of 50 students were given the same test and showed an average score of 83.20. Is there evidence to show that this group ha
Poisson distribution - daisies
The meadow behind FLD was divided into 100 equally large parts. Subsequently, it was found that there were no daisies in ten of these parts. Estimate the total number of daisies in the meadow. Assume that daisies are randomly distributed in the meadow.
Three sigma rule
The height of trees in a given stand is known to be a quantity with a normal probability distribution with a mean value of 15 m and a variance of 5 m². Determine the interval in which there will be tree heights in such a stand with a probability of 90%