Standard deviation - practice problems - page 3 of 6
The standard deviation, symbol sigma σ, is a statistical measure of the variability of a data set. Simply put, it tells us how spread out the values are around the mean (arithmetic mean). How far away most of them are from the mean. It is a non-negative number, defined as the square root of the variance of the data. It therefore has the same dimensions as the data.Variance in statistics is the average of the squares of the deviations from the mean (mean). Variance is also a non-negative number.
The sample standard deviation is defined as the square root of the sample variance. When calculating the sample variance, for n data, only (n-1) independent data are considered.
Direction: Solve each problem carefully and show your solution in each item.
Number of problems found: 114
- Suppose 6
Suppose the life span of a revolutionary light bulb is normally distributed with a mean life span of 70 thousand hours and a standard deviation of 3 thousand hours. If a light bulb is chosen at random: a) what is the probability the life span will be with - 10km race
Joan's finishing time for the Bolder Boulder 10 km race was 1.77 standard deviations faster than the women in her age group. 415 women ran in her age group. Assuming a normal distribution, how many women ran more quickly than Joan? - Z score transformation
The annual salary of an entry-level statistics major (in thousands of dollars) is normally distributed with a mean of 75 and a standard deviation of 12. X ∼ N ( μ = 75, σ = 12 ). What minimum salary should a statistics major aim for to earn amongst the to - The probability The probability that a life bulb will have a more than 682 hours lifetime is 0.9788. The probability that a bulb will have a more than 703 hours lifetime is 0.0051. Find the probability that a bulb will last for more than 648 hours.
- Two sigma
Khail took his math test and scored 88. If the class average was 78 with a standard deviation of 5, what percent of students earned a higher grade than Khail's grade? - A biologist A biologist knows that the average length of a leaf of a certain plant is 4 inches. The standard deviation of the population is 0.6 inches. A sample of 20 leaves of that type of plant given a new type of plant food had an average length of 4.2 inches. At
- An exam - normal distribution Five thousand students take an exam with a mean of 59 and a deviation of 8. How many students will score less than 75?
- The number 5
The number of hours per week the television is turned on is determined for each family in a sample. The mean of the data is 35 hours, and the median is 31.2 hours. Twenty-four families in the sample turned on the television for 20 hours or less for the we - 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?
- Three sigma rule
Stomach weights are normally distributed, with a mean of 1314g and a standard deviation of 113g. State the probability that a randomly selected stomach weighs more than 1118g. (Report the probabilities using at least four decimal places. ) - 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.
- 68-95-99.7 rule
Assume the resting pulse rates for a sample of individuals are normally distributed with a mean of 70 and a standard deviation of 15. Use the 68-95-99.7 rule to find the following quantities. a. Percentage of pulse rates less than 70 b. Percentage of puls - Significance 61784 Determine the interval estimate of the standard deviation of the meantime to find a parking space. We found out from a survey of 200 residents that the average time is one hour and 25 minutes, and the standard deviation is 15 minutes. Use a 1% significanc
- Confidence 61774 What is the smallest number of men we would have to choose to estimate the mean height of men with an accuracy of +, - 0.5cm, and 95% confidence, assuming a standard deviation of 8cm?
- Two methods A teacher wishes to teach verbs to his English class using two methods. He randomly divided the class into two samples of 14 students each. Using Method 1, the students learned an average of 43.8 with a standard deviation of 4.6, while the second group (M
- 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 a result), or the standard deviation of 5 random numbers picked from 1 to 69 in the multi-state PowerBall L - A student 2 A student randomly selected 225 college students and asked whether they had eaten breakfast that morning before coming to campus. Fifty-seven students were at least 25 years old, and 30 had breakfast that morning. Of the 168 students younger than 25, 82 h
- 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. )
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. Four hundred students are randomly selected from the college, and 224 ofDo you have homework that you need help solving? Ask a question, and we will try to solve it. Solving math problems.
