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Sir i am facing trouble solving this question, since I don’t get it how are we calculating the z score in this question.
A normal distribution has a mean of 120 and a standard deviation of 15. 75% of the population is therefore below what value?
50% of the population is below the mean.
Therefore 25% (or 0.25 are between the mean and the value required).
So to arrive at the z-score you need to work backwards in the tables provided and find the number of standard deviations that gives an answer of 0.25.
Have you watched my free lectures on this?
Yes sir i understood that 50% of the population is below the mean, since it’s either 50% below the mean or above the mean, and remaining 25% is between mean and the value required, that means we got that 0.25/25% probability from z score using normal distribution table, and if we check 0.25 in table, it results in z score 0.67, but what I don’t understand is 0.68 is closer to 0.25 as in table 0.68 gives the probability of 0.2517, does rounding off matters in normal distribution questions? That’s it sir, and yes I’ve watched your all lectures on certain topics of f2, they’re very helpful, thank you sir!
No, rounding off does not matter in the exam. Just choose the one that gives the nearest to the figure required 🙂
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