MHB Mean & Std Dev for Norm Dist. Exam Marks - 450 Stud.

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To find the mean and standard deviation of exam marks for 450 students with a normal distribution, the number of first-class students (25) and failed students (90) are key data points. The first-class threshold is set at 60% or more, while the failure threshold is below 30%. This distribution indicates that 335 students scored between 30% and 60%. Calculating the mean and standard deviation requires additional statistical methods or formulas based on these figures. Providing initial calculations or attempts would facilitate more targeted assistance.
wajeehayas
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Assuming that the number of marks scored by a candidate is normally distributed, find the mean and the standard deviation, if the number of first class students(60% or more marks) is 25, the number of failed students(less than 30%marks) is 90 and the total number of candidates appearing for the examination is 450.
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Hello wajeehayas and welcome to MHB! :D

We ask that our users show their progress (work thus far or thoughts on how to begin) when posting questions. This way our helpers can see where you are stuck or may be going astray and will be able to post the best help possible without potentially making a suggestion which you have already tried, which would waste your time and that of the helper.

Can you post what you have done so far?
 

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