Standard deviation - practice problems - page 4 of 6
Direction: Solve each problem carefully and show your solution in each item.Number of problems found: 108
- 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 we obtained an average speed of 62 words per minute 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 phone battery manufacturer claims that his battery lives are approximately normally distributed with a standard deviation equal to 0.9 years. Suppose a random sample of 10 of these batteries has a standard deviation of 1.2 years. Do you think that the s - Confidence Interval
The average grade of 50 senior students in a statistics class is 85, with a standard deviation of 10.2. In comparison, 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 chance, - 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 was given the same test and showed an average score of 83.20. Is there evidence to show that this group has - 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 - 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 estimate 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 the amount of o - 5-number summary
Given the following 5-number summary: 11, 19, 24, 30, 48, which of the statistics cannot be determined? - Bivariate data set
Here is a bivariate data set in which you believe y to be the response variable. x y 51.4 44.8 60.2 46.6 60.1 46.8 45.8 46.3 37.4 41.8 72.4 52.5 60 48.2 67.5 49.5 60.9 49.8 51.1 45.7 62.7 49.6 194.9 84.2 Make a scatter plot of this data. Which point is an - Dataset:
Dataset: 35 22 18 54 22 46 28 31 43 22 14 17 25 19 33 14. 1 Group the data into a grouped distribution using six classes of equal width. 2. Determine the mean, median, and mode using the raw data. 3. Draw an Ogive curve corresponding to the data and use i - Statistical survey
Write TRUE OR FALSE for each question: 1 Standard deviation measures central location. 2. The most frequent observation in a data set is known as the mode. 3 The most passive method of data collection is observation. 4 Access time for secondary data is sh - A mountain climber
A mountain climber plans to buy some rope to use as a lifeline. Which of the following would be the better choice? Explain your choice. Rope A: Mean breaking strength:500lb; the standard deviation of 100lb Rope B: Mean breaking strength: 500lb; the standa - Tallest people a
As a group, the Dutch are amongst the tallest people in the world. The average Dutchman is 184 cm tall. If a normal distribution is appropriate, and the standard deviation for Dutchmen is about 8 cm, what is the percentage of Dutchmen who will be over 2 m - The raw
The raw data presented here are the scores (out of 100 marks) of a market survey regarding the acceptability of a new product launched by a company for a random sample of 50 respondents: 40 45 41 45 45 30 30 8 48 25 26 9 23 24 26 29 8 40 41 42 39 35 18 25 - Corresponding 33321
The following data on the height and the corresponding number of pupils were found in the measurement of 63 pupils: 159cm-1,161cm-1,162cm-2,163cm-1,164cm-2,165cm-2,166cm-3,167cm-2,167cm-3 6,172cm-7,173cm-9,174cm -5,175cm-2,177cm-1,178cm-4,179cm-2,181cm-1, - Statistical XY file
Year; money spent on advertising; profit (three values each row) 2008 2 12 2009 5 20 2010 7 25 2011 11 26 2012 15 40 1. draw a scatter diagram depicting the data. 2. calculate the Pearson's correlation coefficient. 3. determine the linear regression equat - Marketing
Year; money spent on advertising; profit 2008 2 12 2009 5 20 2010 7 25 2011 11 26 2012 15 40 1. draw a scatter diagram depicting the data. 2. calculate the Pearson's correlation coefficient. 3. determine the linear regression equation. - Complaints
The table is given: days; complaints 0-4; 2 5-9; 4 10-14; 8 15-19; 6 20-24; 4 25-29; 3 30-34; 3 1.1 What percentage of complaints were resolved within two weeks? 1.2 calculate the mean number of days to resolve these complaints. 1.3 calculate the modal nu
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