# Standard deviation - practice problems

#### Number of problems found: 74

- 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. - Quartile statistics

Use the following data which was obtained from a study of weights of adult men to answer problems: Mean ; 192 lb ; First quartile ; 178lb Median; 185lb ; Third quartile ; 232 lb Mode ; 180 lb ; 86th percentile ; 239 lb Standard Deviation ; 23lb; ; a) What - Z-score test

The weights of the fish in a certain lake are normally distributed with a mean of 11 lb and a standard deviation of 6. If 4 fish are randomly selected, what is the probability that the mean weight will be between 8.6 and 14.6 lb? Your answer should be a d - Summaries

A specialist teacher observes time taken by each of the students with learning disabilities to complete a psychological task. She summaries the times using the following: Time Taken(mins) ; 1-5; 6-10; 11-12; 16-20 No. of Student ; 2 ; 4 ; 12; 4 Using the - A sample

A sample of 10 randomly selected students revealed the following grades in Business Statistics first test (in a marking scale of 0 to 100): 79, 63, 60, 45, 55, 58, 59, 62, 40, 68. Examine the data using groups and presenting: a) the Histogram of the absol - 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 for her age group. There were 415 women who ran in her age group. Assuming a normal distribution, how many women ran faster than Joan? - Z score transformation

The annual salary of an entry level statistics major (in thousands of dollars) is normally distributed with mean of 75 and standard deviation of 12. X ∼ N ( μ = 75, σ = 12 ). What is the minimum salary a statistics major should aim for in order to earn am - The probability

The probability that a life bulb will have a life time of more than 682 hours is 0.9788. The probability that a bulb will have a life time of more than 703 hours 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 an 88. If the class average was 78 with a standard deviation of 5, what percent of students earned a grade that was HIGHER 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 inch. 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 le - An exam - normal distribution

5000 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 that 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 of the families in the sample turned on the television for 20 hours or less - 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

Stoach weights are normally distributed, with mean 1314g and standard deviation 113g. State the probability that a randomly selected stoach weighs more than 1118g. (Report the probabilities using at least 4 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 - 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 two methods of teaching verbs to his English class. He divided the class randomly 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 (Meth - 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

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