Confidence Intervals

lvgirle · 11-02-2009, 01:13 PM

A survey of 64 random sports viewers revealed that 32 of them watched the football game. Construct a 99% confidence interval estimate for the true proportion of all sports viewers who watched that game.

So far I have n = 40
And I'm supposed to use the equation x bar - E, x bar + E
E = Z σ/2 (σ / square root of n)

I'm not sure which number I'm supposed to look up in the Z-scores table and where to plug in which numbers?! Very confused and I have 2 hw problems with this in it.

The other is as follows:
A sample of 36 patrons of a local bar were asked how many hours per week they spent socializing at the bar. The resulting answers averaged 10hrs with a standard deviation on 2.4hrs. Construct a 95% confidence interval estimate for average time spent socializing by all the patrons?

The problems are similar but both give different information. I'm confused about how to set up each problem?! I appreciate any help.

allinorfold · 11-02-2009, 08:19 PM

In the first one, why do you say n=40? n=amount of people in sample=64.
x bar would equal 32/64=.5.
You're Z value is obtained from the tables. This is a two-taled interval so .005 must be the probability you search for in th standard stats tables(i think its table 4).

11-02-2009, 01:13 PM	#1
lvgirle Junior Member Join Date: Nov 2009 Posts: 1 Thanks: 0 Thanked 0 Times in 0 Posts	Confidence Intervals A survey of 64 random sports viewers revealed that 32 of them watched the football game. Construct a 99% confidence interval estimate for the true proportion of all sports viewers who watched that game. So far I have n = 40 And I'm supposed to use the equation x bar - E, x bar + E E = Z σ/2 (σ / square root of n) I'm not sure which number I'm supposed to look up in the Z-scores table and where to plug in which numbers?! Very confused and I have 2 hw problems with this in it. The other is as follows: A sample of 36 patrons of a local bar were asked how many hours per week they spent socializing at the bar. The resulting answers averaged 10hrs with a standard deviation on 2.4hrs. Construct a 95% confidence interval estimate for average time spent socializing by all the patrons? The problems are similar but both give different information. I'm confused about how to set up each problem?! I appreciate any help.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

11-02-2009, 08:19 PM	#2
allinorfold Junior Member Join Date: Oct 2009 Posts: 18 Thanks: 1 Thanked 1 Time in 1 Post	In the first one, why do you say n=40? n=amount of people in sample=64. x bar would equal 32/64=.5. You're Z value is obtained from the tables. This is a two-taled interval so .005 must be the probability you search for in th standard stats tables(i think its table 4).