cnu115
On an exam, a class ended with a mean raw score of 80 with standard deviation of 10. The distribution of grades in the class was approximately normal. If the teacher wants to give "A" to the top 25th percentile (top 25%) of the class, what is the lowest raw score we could get and still get an "A" on the exam?
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dan815
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cnu115
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standard deviation of 10
dan815
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lol i mean how many deviation points wud u have to travel, to be left with only 25% area on the right side
dan815
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look up the probability distribution graph numbers
cnu115
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Sorry sir, I could not follow you. Could you please explain
dan815
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look at that and see at what standard deviation you have to be to be left with only 25% area on the right side
dan815
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cnu115
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Is it 21% with 0.8 standard deviation?
cnu115
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It is only one standard deviation point above the mean is to be covered. Isn't it? Other please explain
dan815
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dan815
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how much more deviation does she have to go to cover upto 75%
dan815
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look at that chart and figure it out
dan815
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dan815
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its somewhre inbetween 0.5 and 1
dan815
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id say around 0.75
dan815
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so 0.75 of 10 = ? 7.5 marks
dan815
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then 87.5 should be the marks she needs to set it at
dan815
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im just estimating values here, im sure u got some formulas to calculate the exact z values and stuff
dan815
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cnu115
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This Z values I am not aware sir. I am just browsing about this
dan815
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this will give u more accurate vlaue
dan815
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dan815
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dan815
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dan815
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dan815
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dan815
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cnu115
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cnu115
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what is this equation you have used
dan815
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5.6/15
dan815
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because
dan815
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look at the chart
dan815
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at 0.5 deviation on right how much percent have you covered?
cnu115
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and how did you get 0.37
dan815
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do you know the answer already
cnu115
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????? 5*6/15=0.37 ????
dan815
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whats the answer supposed to be
dan815
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its 5.6 not 5 * 6
dan815
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i cant help you if u arent answering my questions
cnu115
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No. Idon't know the answer
dan815
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then dont bother with stuff
dan815
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first understand the graph
cnu115
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I want to know more about this Z score
cnu115
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Ok sir
dan815
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the graph is pretty self explanatory and questions about it?
dan815
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any questions?
cnu115
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just a second sir,
cnu115
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Now it is clear. But one question. May I ask
cnu115
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Why did you divide by 15. It is only 14 parts. Right
cnu115
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Sorry. Now I have fully understood.
cnu115
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It is not the 14 parts. It is the area of that part.
cnu115
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Thank you very much explaining in detailed manner
cnu115
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Thanks for your patience and analysing for a lehman.
Musadiq
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Mean 80 standard deviation 10 z=-0.67
X=73.3
Musadiq
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mine answer is 73.3 marks min to get A
Musadiq
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you have to take Z value -0.67
dan815
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musadiq no try taking 0.67 Z
Musadiq
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well table value is 0.67 that's lies at left side !