Standard deviation + probability - practice problems
Number of problems found: 35
- 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? - 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 - 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. - 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? - Distributions 82068
Javelin throwers Anna and Barbora have average throw lengths of 67 m and 75 m, respectively, and standard deviations of 6 m and 3 m, respectively. Assume that the throw lengths have independent normal distributions. Calculate the probability that Anna thr - Distribution 82042
Assume that the IQ in the population follows a normal distribution with a mean of 100 points and a standard deviation of 10 points. With what probability among 15 randomly selected people: a. Is there anyone with an IQ above 130 points? b. Are there at le - The average 7
The average lifespan for cricket is 90 days, with a standard deviation of 13 days. If we assume that the lifespan of cricket is normally distributed, a. What is the probability a randomly selected cricket has a lifespan of fewer than 75 days? b. What is t - 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 - 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 - 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. - 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? - 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. - Sample Proportion
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 of - Suppose 4
Suppose that 14% of all steel shafts produced by a certain process are nonconforming but can be reworked (rather than having to be scrapped). Consider a random sample of 200 shafts, and let X denote the number among these that are nonconforming and can be - Rich retirement
Health care issues are receiving much attention in both academic and political arenas. A sociologist recently surveyed citizens over 60 years of age whose net worth is too high to qualify for government health care but who have no private health insurance - Three sigma rule
The height of trees in a given stand is known to be a quantity with a normal probability distribution with a mean value of 15 m and a variance of 5 m². Determine the interval in which there will be tree heights in such a stand with a probability of 90% - A machine
A machine produces steel rods of normally distributed length, the mean length and the standard deviation being 50.0 cm and 0.5 cm, respectively. The rods do not conform to safety standards if they are either shorter than 49.1 cm or longer than 50.7 cm in - Statistical survey
Write TRUE OR FALSE for each question: 1 Standard deviation measures central location. 2. The most frequent observation in a data set is known as the mode. 3 The most passive method of data collection is observation. 4 Access time for secondary data is sh
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