Question

What is the probability of obtaining a z-score less than 0.75 if the distribution of scores is normal?

1. ThanhThu
0.7734 or 77.34 %
• We can convert any normal distribution to a normal distribution  to find the probabilities and apply the properties of the  normal. To do this, we use the z score.
• The Z value (or sometimes called the Z-score or simply Z) represents the number of standard deviations between an observation and the mean of a data set.
• For any normal random variable, if you find a Z-score for a value (i.e. normalize the value), the random variable will be transformed into a standard random variable and you can find the probability by using  standard tables.
If the area under the standard curve to the right of the z-value is 0.75, then the area under the curve to the left of that z-value is 0.25.
Using the normal table (z), find 0.2500 of the probabilities. The closest zone to 0.2500 is 0.2514. The z value associated with this is -0.67.
The probability that a randomly selected z is greater than -0.67 is about 0.75.