# Standard deviation - practice problems

Direction: Solve each problem carefully and show your solution in each item.#### Number of problems found: 110

- Fish service

According to a report by the U. S. Fish and Wildlife Service, the mean length of six-year-old rainbow trout in the Arolik River in Alaska = 484.6 millimeters with a standard deviation = 31.2 millimeters. Assume these lengths are normally distributed. What - Bell curve

A company has a policy of retiring company cars; this policy looks at the number of miles driven, purpose of trips, style of car, and other features. The distribution of the number of months in service for the fleet of cars is bell-shaped and has a mean o - IQ scores

IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. What percentage of the population scores higher than 125 on an IQ test? - The usage

The battery usage time installed in a particular smartphone has a Normal distribution with a mean of 25.2 hours and a standard deviation of 7.5 hours. What is the probability of usage time greater than 32?

- Squared deviation

Given the data from the problem (sample data: 23, 27, 35, 44), find the sum of the squared deviations (the numerator of the fraction under the square root in the formula). In finding the number, round all calculations to 2 decimals (if you carry more or f - Suppose 12

Suppose in a physics test involving 30 students, and four scored 75%, eight scored 60%, twelve scored 50%, and six scored 30%. Calculate the mean of the group and the standard deviation. - The mass 3

The mass of certain types of cabbage is normally distributed with a mean of 1000 g and a standard deviation of 0.15 kg. In a batch of 800 cabbages, estimate how many a mass between 750g and 1290g. - Coefficient of skewness

For the data set whose Karl Pearson's Coefficient of skewness = -2.25, variance is 16, and Mean is 35, then its median value will be: - A sample variance

Calculate the value of the sample variance. −8,−8,−3,13,4,−8,10,8

- Compare variation

The mean blood pressure was 135 mmHg in a series of adults with a standard deviation of 10 mm Hg. In the same series, the mean height was 170 cm with a standard deviation of 6 cm. Find which character shows a greater variation (write A or B). - Q10 - investigate

A nutritionist who investigates fruits reported that the average weight of a raspberry is 4.4 g with a standard deviation of 1.28 g. What is the probability that a randomly selected raspberry would weigh less than 3.1 grams? Let X represent the weight of - A random

A random sample of 225 nails in a manufacturing company is gathered. The engineer specified that the specified length of a nail must be 8 cm having a standard deviation of 0.04 cm. It shows from the sample that the average length of the nails is 8.055 cm. - The number 7

The number of faulty units in a carton of a particular product is known to be normally distributed with a Mean of 10 and a variance of 25. What portion of a given carton of the product is expected to contain___ faulty units? (I) less than 8 (ii) more than - Lengths 6

Lengths of 130 tubes are measured. The arithmetic mean is 17.27 cm, and the standard deviation is 1.2 cm. How many tubes do have a length: a) between 16.5 cm and 18.1 cm b) greater than 17 cm

- Bulb life

Tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a standard deviation of 75 hours. Find the probability that a randomly selected light bulb will last between 675 and 900 hours. - Z-score calc

What is the Z Score for the following numbers: X is 16, and data for the population mean, and the standard deviation is 196, 193, 79, 30, 29, 81, 25, 21, 164 Level of difficulty = 2 of 2 Please format it to 2 decimal places. - Z-score 3

A random variable X has a mean of 4 and a standard deviation of 2. What is the corresponding z-score for x = 7? - 3 sigma

Students' performance scores in a statistic test have a mean of 70 and a standard deviation of 4.0. The scores obtained can be modeled by a normal distribution. Find the probability that the score of a randomly selected student is i. more than 80 marks ii - The profit 3

An investment's profit (or loss) is normally distributed with a mean of $11,200 and a standard deviation of $8,250. What is the probability of a loss rather than a profit?

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