Question

Easy Statistics, solved some, but need some help too! Thanks!

Answer 1

John is an expert horseshoe thrower who only misses 15% of the time. Choose the expression that correctly represents the probability John will miss fewer than 50 times if he throws 400 horseshoes.

normalcdf(-E99,50,60,7.14)

normalcdf(50,E99,60,7.14)

normalpdf(-E99,50,400,7.14)

normalpdf(-E99,50,60,7.14)

normalcdf(-E99,50,400,7.14)

Answer 2

@perl

Answer 3

Are you familiar with binomial probability distributions?

Answer 4

not really!

Answer 5

first find the mean and st. dev for a binomial distribution
mean = n*p
st. dev = sqrt( np (1-p))

Answer 6

well you'll start there and then use a normal distribution to approximate it. What's odd is that they didn't account for the continuity correction factor. Oh well

Anyways, we are given

n = 400 trials
p = 0.15 is the probability of success
q = 1-p = 1-0.15 = 0.85 is the probability of failure

use these values to compute the mean mu and standard deviation sigma

mu = n*p = 400*0.15 = 60
sigma = sqrt(n*p*q) = sqrt(400*0.15*0.85) = 7.14

Answer 7

wow thanks guys, now I can do the rest of these problems now that i have an example!