7. In a specific Massively Multiplayer Online Role-Playing Game (MMORPG), you ca

Question

7. In a specific Massively Multiplayer Online Role-Playing Game (MMORPG), you can earn items by mining. When you find a suitable place to mine, a screen pops with a list of items and a percentage for each item. You get four swings of your pickaxe; for each swing, the percentage indicates the chance of getting an item on the current swing. Suppose the item you want has a 80% chance of dropping on any given swing. What is the probability of not getting an item in exactly three out of the four attempts? 8. Accidents, suicides, and homicides are the leading causes of death for young adults. Here is a two-way table of probabilities of violent deaths in a recent year among people aged 20 to 24 years: Female Male Total Accidents .1289 .45805869 Homicides0324 2036.2360 0245.1526.1771 Suicides Total 1858 .81421 Note that the intersection of two variables in the table give the "and" prob- abilities, ie.' P(homicide and male) .2036, while the row and column totals give the probabilities for the individual variables, i.e. P(accident) - .5869 and P(male)-8142. Find the following: (a) Find the probability that the victim was male given that the victim committed suicide. (b) Find the probability that the victim died in an accident given that the victim was female 9. Suppose that a particular exam follows a normal distribution with mean score 69.83 and standard deviation 24.15 (a) What score is required to be in the 80th percentile on this exam? (b) What range of scores represent 95% of all scores on this exam?

Explanation / Answer

9)

Mean = 69.83
SD = 24.15

a. P( X<=c) = .80
Z for 80th percentile is .84
So, (c-69.83)/24.15 = .84
c = 24.15*.84+69.83 = 90.116

b. Range of scores that represent 95% of all scores on this exam?
So, the Z is +/- 1.96 such that the area around the mean is 95%. Hence we will
find the X values for Z = +/- 1.96

So, c = 69.83 - 1.96*24.15 to 69.83 + 1.96*24.15
=22.496 to 117.164

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