Comparing + normal distribution - practice problems
Number of problems found: 9
- 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. - 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? - Distribution 81063
The weight of a loaf of bread should be 900 g. Loaves whose weight differs by more than 30 g from this value must be rejected. Determine the probability that a loaf is rejected if its weight has a normal distribution N(900,40). - 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 - 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? - 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 - Performance comparing
A standardized test was administered to thousands of students with a mean score of 85 and a standard deviation of 8. A random sample of 50 students was given the same test and showed an average score of 83.20. Is there evidence to show that this group has - A mountain climber
A mountain climber plans to buy some rope to use as a lifeline. Which of the following would be the better choice? Explain your choice. Rope A: Mean breaking strength:500lb; the standard deviation of 100lb Rope B: Mean breaking strength: 500lb; the standa - Tallest people a
As a group, the Dutch are amongst the tallest people in the world. The average Dutchman is 184 cm tall. If a normal distribution is appropriate, and the standard deviation for Dutchmen is about 8 cm, what is the percentage of Dutchmen who will be over 2 m
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