Standard deviation - practice problems - page 3 of 7
Task: Work through each problem with care and demonstrate your solution process for each one.Number of problems found: 128
- Z-score test
The fish weights in a certain lake are normally distributed with a mean of 11 lb and a standard deviation of 6. If four 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 decim - Summaries
A specialist teacher observes the 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 - A sample
A sample of 10 randomly selected students revealed the following grades in Business Statistics first test (on 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 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
- Test of robots We have an automatic line for producing kitchen robots. We want to help by Wald's test to test whether the share of defective robots does not exceed 5% by more than 1%. We can test up to 200 robots at once. The costs of the performed test are 50 Kč on the
- 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?
- Probability
A restaurant always counts the cash register at the end of the day so that the employees can divide their tips. It has been found that the daily tips follow a normal distribution with a mean of €130 and a standard deviation of €60. What is the probability - 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 - Test time percentage 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 1314 g and a standard deviation of 113 g. State the probability that a randomly selected stomach weighs more than 1118 g. (Report the probabilities using at least four decimal places. ) - Banker client probability 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 - Parking time interval 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
- Height estimation men What is the smallest number of men we would have to choose to estimate the mean height of men with an accuracy of +, - 0.5 cm, and 95% confidence, assuming a standard deviation of 8 cm?
- 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
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