If scores on an exam are normally distributed with a mean of 80% and a standard deviation of 10%, what would a score of 90% be in Z-scores (e.g., how many standard deviations is this score above or below the mean)?

Z=-1.5 Z=-1.0 Z=0 Z=1.0 Z=1.5

Question

If scores on an exam are normally distributed with a mean of 80% and a standard deviation of 10%, what would a score of 90% be in Z-scores (e.g., how many standard deviations is this score above or below the mean)?

Z=-1.5 Z=-1.0 Z=0 Z=1.0 Z=1.5

anonymous · Answer

+1.0 right?

amistre64 · Answer

z = (x-mean)/sd

amistre64 · Answer

so yes, +1 sd looks fine

anonymous · Answer

ahahaha.. ti looks so easy to be real!! ;p get ready a quiz game begining ;)

anonymous · Answer

$$\bf z=\frac{ x-\mu }{ \sigma }$$Now plug in 90% for 'x', 80% for mean and 10% for S.D to get the z-score:$$\bf z = \frac{ 90-80 }{ 10 }=1$$Now look this up on a z-score table and so the probability of getting up to 90% would be:$$\bf P(z<1)=0.8413$$

anonymous · Answer

oh u just wanted to know the z-score..lol

amistre64 · Answer

lol, ... the answer to a question that was never asked ;)

anonymous · Answer

genius you are too genius for these questions ;p...  you are for next level questions just wait ;p

anonymous · Answer

@amistre64 I always assume that a z-score question is asking for the probability as well since it's usually the case with most questions...lol