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Hello, Can you please do a video on number 30 from the chapter 8.4 Homework. The test stat was 1.58 and it was a left side test. We look at the Z-table under 1.58 and get .4429, so the P-value would be .5-.4429 =.0571?? in the video i saw that you did both sides of the curve rather then one in like all the other examples can you explain why please?

Posted to STATS 1 on Thursday, April 24, 2014   Replies: 2

Professor Mcguckian
04/24/2014
4:54 PM EST

Hi Allison,

As you stated, it is a left-tailed hypothesis test since Ha has a < symbol.   This means we have to find the area to the left of the test statistic in order to find the p-value, but notice that 1.58 is positive. The test stat, 1.58, is on the right side of the curve. The area to the left of 1.58 is greater than 50% since 1.58 is on the right half of the curve.  When we look up 1.58 we get 0.4429 for the area from 1.58 to 0.  We then have to add 0.5000 to account for the remaining left half of the curve.  The final answer is 0.9429. I'll add a video soon.

Hope that helps,

Professor McGuckian

Professor Mcguckian
04/24/2014
6:54 PM EST