Final answer:In a standard normal distribution (Z),the Z-scorecorresponding to an area of 0.9 under the normal curve is approximately 1.28. This score indicates that it is 1.28 standard deviations above the mean. More complicated Z-score calculations can be performed using calculators or computer programs.Explanation:The question pertains to the calculation of probabilities based onstandard normal distributionorZ distribution. A standard Z distribution is represented as Z ~ N(0, 1), where the mean(µ) is 0 and the standard deviation (σ) is 1.The value you're looking for is the Z-score, which corresponds to an area of 0.9 under the normal curve. The Z-score is a standardized value that indicates how many standard deviations a particular data point is from the mean.To find the Z score, one usually refers to a Z table, also known as a standard normalprobability table. From the Z table, we can observe that a Z score of approximately 1.28 corresponds to an area of 0.9. In simpler terms, a score of 1.28 is 1.28 standard deviations above the mean of a standard distribution.For more complex calculations involving Z-scores, calculators or computer programs can be utilized. For instance, the from invNorm(n, µ, σ) function can be used to find critical values.Learn more aboutStandard Normal Distributionhere:brainly.com/question/30390016#SPJ11...

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