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December 26, 2019 at 8:40 pm
Hi sir, Please explain this questions. Q1)A normal distribution has a mean of 75and a variance of 25. what is the upper quartile of this distribution? Q2)A normal distribution has mean of 150,and a standard deviation of 20. 80% of the distribution is below which of the following (approximately)?
John Moffat says
December 27, 2019 at 7:34 am
In future please ask this kind of question in the Ask the Tutor forum, and not as a comment on a lecture.
For the first question you need to find the value that has a probability of 25% (0.25) of being above the mean. For the second question you need to find the value that has a probability of 80 – 50 = 30% (0.30) below the mean.
In both cases you need to work backwards in the tables to find the number of standard deviations (the z score) in the way I explain in the lectures.
September 6, 2019 at 9:56 am
what if the z score for 10 and 10.4 is 2. 96 then the area from curve table that we would choose is 2.906 ‘s = 0 .4985 ?
September 6, 2019 at 9:07 am
Hi SIr, Can you please explain again what you meant by area of bar is proportional to frequency. I cant seem to understand it
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