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Course Documents

Chapter 1 - Intro

Chapter 2 - Methods for Describing Sets of Data

Chapter 3 - Probability

Chapter 4 - Discrete Random Variables

Chapter 5 - Normal Random Variables

Chapter 6 - Sampling Distributions

Chapter 7 - Confidence Intervals

Chapter 8 - Tests of Hypothesis: One Sample

Chapter 9 - Confidence Intervals and Hypothesis Tests: Two Samples

Sample Exam I: Chapters 1 & 2

Sample Exam II: Chapters 3 & 4

Sample Exam III: Chapters 5 & 6

Sample Exam IV: Chapters 7 & 8

Ask the Professor Forum

Hello Professor,
Can you explain the process for the homework in 4.4 number 23 please?
I only get 30 Choose 15, but I dont know my p or my q.
Please help.

Thank you

Posted to STATS 1 on Sunday, October 20, 2013   Replies: 2

Professor Mcguckian
1:19 PM EST

Hi Christina,

For every binomial probability problem, we need to identify n, x, and p. 

n represents the number of trials, so in this case it is the number of flips of the coin.

x represents the number of successes we have. In this problem we are looking to get heads, so heads is our success.  Thus, we will say x = 15 because we want 15 heads, and x is the number of successes. 

Lastly, we need to determine p. p is our probability of success.  Well, if heads are what we want, heads are our success, so we need the probability of a heads turning up on a single flip of the coin. That probability is 1/2 =0.50 because there is one head on the coin and two total sides. **Remember q = 1 - p, so q = 1 - 1/2 = 1/2 = 0.50.

Then we just turn to the formula: nCx p^x * q^(n-x) = 30C15 * 0.50^15*0.50^15

I hope that helps,

Professor McGuckian

2:29 PM EST

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