# Standard deviation - practice problems

Direction: Solve each problem carefully and show your solution in each item.#### Number of problems found: 92

- 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? - Dataset

Data: 11,15,11,16,12,17,13,21,14,21,15,22 Find dispersion of a given dataset. - 5-number summary

Given the following 5-number summary: 11, 19, 24, 30, 48, which of the statistics cannot be determined? - Dispersion 3335

What is the value of the variance of the data in the file if the calculated standard deviation = 2? a) Dispersion = 6 b) Dispersion = 4 c) Dispersion = 9 d) Dispersion = 2 - 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 - Z score transformation

Suppose a distribution has a mean µ = 8 and standard deviation σ = 4. What is the value of x if it is z = +1.50? - Dataset 3

Given dataset: 31, 28, 31,30,31,30,31,31,30,31,30,31 1. Construct a frequency table. 2. Construct a histogram. 3. Compute the mean. 4. Compute the median. 5. Find the mode. 6. Compute the midrange. 7. Compute the standard deviation. - Distribution 6399

For the statistical file: 2.3; 3.4; 1.8; 3.2; 3.2; 1.9; 3.3; 4.5; 4.3; 5.0; 4.8; 4.3; 4.3; 1.9 Determine the sample variance and the median, and from the empirical distribution function, determine P (2.1 - Probability 64174

The banker deals, on average, with five clients a day. Find the probability that the number of clients (in one day) will be greater than 4. - Variability 29933

In September, students missed the following number of lessons: Girls: 2; 0; 7; 8; 2; 2; 4; Boys: 4; 4; 0; 3; 10; 3; 8; Compare the variability of both statistical files. - Alopecia

Medical literature indicates that 45% of men suffer from alopecia. For a random sample of 8 men, calculate the probability that: (a) exactly four men suffer from alopecia. (b) at most, two men suffer from alopecia. - Distribution 67074

The time required to complete the test has a normal distribution with a mean of 50 minutes and a standard deviation of 10 minutes. What percentage of students take the test within 30 minutes? - The Uniform Distribution

The number of tickets purchased by an individual for Beckham colleges holiday music festival is uniformly distributed random variable ranging from 5 to 12. What is the standard deviation? - IQR and range

The times spent in minutes by 20 people waiting in a queue at the bank for a teller were: 3.4, 2.1, 3.8, 2.2, 4.5, 1.4, 0,0, 1.6, 4.8, 1.5, 1.9, 0, 3.6, 5.2, 2.7, 3.0, 0.8, 3.8, 5.2, Find the range and interquartile range of the waiting times. - 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 does have a length: a) between 16.5 cm and 18.1 cm b) greater than 17 cm - 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? - Controller

Output Controller of the company in the control of 50 randomly selected products found that 37 of them had no defects, eight had only one flaw, three had two defects, and two products had three defects. Determine the standard deviation and coefficient of - Life expectancy

The life expectancy of batteries has a normal distribution with a mean of 350 minutes and a standard deviation of 10 minutes. What is the range in minutes 68% of the batteries will last? What is the range in minutes? How long will approximately 99.7% of b - The probability

The probability that a life bulb will have a lifetime of more than 682 hours is 0.9788. The probability that a bulb will have a lifetime of more than 703 hours is 0.0051. Find the probability that a bulb will last for more than 648 hours. - Distribution 6282

The waiting time in the buffet is governed by the normal distribution with a mean value of 130 seconds and a variance of 400. What is the probability that someone will wait less than a minute and a half?

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