# Standard deviation - practice problems

#### Number of problems found: 49

- Two methods

A teacher wishes two methods of teaching verbs to his English class. He has divided the class randomly into two samples of 14 students each. Using Method 1, the students learn an average of 43.8 with a standard deviation of 4.6, while the second group (Me - Two fertilizers

Jason is testing two fertilizers, Grow Well and Green Grow, so he went to a nursery and bought 50 tomato plants of the same variety. He planted all 50 plants in an identical environment. He then administered Grow Well to 25 of the tomato plants and Green - Compare distributions

Which would you expect to be larger, the standard deviation of 5 random numbers picked from 1 to 47 in the California Super Lotto (CSL - write 1 as result), or the standard deviation of 5 random numbers picked from 1 to 69 in the multi state PowerBall Lot - A student 2

A student randomly selected 225 college students and asked them whether they ate breakfast that morning before coming to campus. There were 57 students that were at least 25 years old, of which 30 had breakfast that morning. Of the 168 students that were - Z-score

The mean adult male pulse rate is 67.3 beats per minute with a standard deviation of 10.3. Find the z-score for an adult male’s pulse rate of 75. (Round the z-score to two decimal places. ) - Sample Proportion

In a California community college, 60% of students will transfer to a college in the CSU system. The number of students in a sample who will transfer follows a binomial distribution. 400 students are randomly selected from the college and 224 of them will - 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 - 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 eight manufacturing companies are: 17 65 117 206 172 181 221 94 What is the lowest and highest market - 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 unemployment rate: 0.5 1 1.5 2 2.5 3 in % (percent). Determine the two-sided confidence interval for the var - 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 - 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% - A machine

A machine produces steel rods of normally distributed length; the mean length and the standard deviation being 50.0 cm and 0.5 cm respectively. The rods do not conform to safety standards if they are either shorter than 49.1 cm or longer than 50.7 cm in l - Five number summary

Find the five-number summary for these data and make a boxplot. 14,5,12,19,2,35,5,4,3,7,5,8 - Confidence interval

A food testing laboratory in Abu Dhabi has been commissioned to carry out an estimate of the amount of olive oil contained in 1-gallon tins purchased from a range of international olive oil producers. The manufacturers state that the standard deviation of - 5-number summary

Given the following 5-number summary: 11, 19, 24, 30, 48 which of the statistics cannot be determined?

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