Suppose you take the SAT test and the ACT test. Not using the chart they provide, can you directly compare your SAT Math score to your ACT math score?

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Presentation transcript:

Suppose you take the SAT test and the ACT test. Not using the chart they provide, can you directly compare your SAT Math score to your ACT math score? Why or why not? We need to standardized these scores so that we can compare them.

z score Standardized score Has  = 0 &  = 1

Let’s explore... Suppose the mean and standard deviation of a distribution are  = 50 &  = 5. If the x-value is 55, what is the z-score? If the x-value is 45, what is the z-score? If the x-value is 60, what is the z-score? So what does the z-score tell you? 1 2

What do these z scores mean?  below the mean 1.8  above the mean 6.1  above the mean 4.3  below the mean

Jonathan wants to work at Utopia Landfill. He must take a test to see if he is qualified for the job. The test has a normal distribution with  = 45 and  = 3.6. In order to qualify for the job, a person can not score lower than 2.5 standard deviations (z score) below the mean. Jonathan scores 35 on this test. Does he get the job? No, he scored 2.78 SD below the mean

Sally is taking two different math achievement tests with different means and standard deviations. The mean score on test A was 56 with a standard deviation of 3.5, while the mean score on test B was 65 with a standard deviation of 2.8. Sally scored a 62 on test A and a 69 on test B. On which test did Sally score the best? She did better on test A.