Download 18E Notes-4.notebook

18E Notes­4.notebook
June 03, 2016
Real­life data (with GDC) ­
normcdf(lower value, upper value, μ, σ)
Ex. Average height of people in a town is 170 cm, and the standard deviation of the heights is 10 cm.
a) How many standard deviations is 165 cm from the mean?
What is the probability that a randomly selected resident is...
b) shorter than 165 cm?
c) between 180 cm and 190 cm tall?
d) taller than 176 cm?
e) If 10 people are randomly chosen, what is the probability that more than 5 are taller than 176 cm?
f) If 10 people are randomly chosen, what is the probability that less than 3 are taller than 176 cm?
Jan 13­5:40 AM
Example: The weights of adult male African elephants are normally distributed with a mean weight of 11,000 pounds and a standard deviation of 900 pounds.
a) Find the probability that an elephant weighs more than 12,000 pounds.
b) Find the probability that an elephant weighs less than 7000 pounds. c) Find the probability that an elephant weighs between 9000 and 11000 pounds.
Jun 1­10:33 AM
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18E Notes­4.notebook
June 03, 2016
Jun 2­11:29 AM
18E ­ Inverse Normal Distribution
Use "InvNorm" when you know the probability.
InvNorm(probability) ­ gives you the z­value.
InvNorm(prob, mean, stand. dev.) ­ gives the x­value.
Find the value of z for each problem
2) P(Z > z) = 0.6
1) P(Z < z) = 0.547
3) P(Z > z) = 0.05
Feb 28­3:39 PM
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18E Notes­4.notebook
June 03, 2016
If X~N(20,16), find the value of x for which
1) P(X < x) = 0.65
2) P(X > x) = 0.96
3) P(X > x) = 0.3
Feb 28­12:14 PM
Ex. 1 On an exam, 85% of the students pass. μ = 55 and σ = 4. What is the lowest score a student can get to pass?
Ex. 2 The mean lifetime of a light bulb is 18 months.
The chances that the bulb will not last 10 months is 0.05. What is the standard deviation?
Jan 15­6:59 AM
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18E Notes­4.notebook
June 03, 2016
Ex. 3 The average weight of a group of people is 69.5 kg. 13% of them weigh at least 72.1 kg. What is the standard deviation?
Ex. 4 A class of students has an average grade of 82%. If the standard deviation of the grades is 7 percentage points, between what two percents do the middle 75% have? Feb 28­3:48 PM
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