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ASK THE PROFESSOR FORUM

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

Hi professor. I keep getting stuck in the same problems. My confusion is when I watch the videos and it display how to do the work on a graphing calculator. Could you please go through problem 58 from 7.6, and show me the steps without the graphing calculator? I could do the earlier problems from that section but 58 and the following few problems Im struggling with when the n is given instead of the ^P .

Posted to STATS 1 on Tuesday, December 9, 2014   Replies: 2


Professor Mcguckian
12/09/2014
2:31 PM EST

Hi Reina,

Use the following data to form a confidence interval for the proportion: n = 3896, x = 702, Clevel = 95%

Step 1: Data n = 3896, x = 702, Clevel = 95%

find p-hat = x / n = 702 / 3896 = 0.1802

q - hat = 1 - p-hat = 1 - 0.1802 = 0.8198

alpha = 1 - CL = 1 - 0.95 = 0.05

Step 2: Critical value Za/2 = Z0.025 = (look up 0.025 on the t-table, then go down to the bottow of that column, the last value is your critical value) = 1.96

Step 3: Margin of Error: E = Za/2*SquareRoot(p-hat* q-hat / n) = 1.96*SquareRoot(0.1802*0.8198 / 3896) = 0.01207

Step 4: (p-hat - E, p-hat + E) = (0.1681, 0.1923)

So, we are 95% confident that the population proportion is between 16.81% and 19.23%. 

Hope that helps,

Professor McGuckian


.
12/09/2014
3:13 PM EST
yes! thank you so much!

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