# Test Yourself

## True or False

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**True**

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**True**

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**True**

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**True**

This converts the value to units of standard deviation away from the mean

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**True**

It is very useful for making comparisons across different measurement constructs or domains because we are comparing things on the same scale, where the value of each observation reflects the distance from the mean in units of standard deviation.

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**False**

**A Z-transformed variable will have a mean of 0 and SD of 1.**

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**True**

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**False**

**It can flag outliers but we’d normally only flag observations > 3 or >4SD from the mean as these lie in the outer 0.3% of a distribution. We'd expect about a third of our observations to lie outside 1SD from the mean, so not a cut off for outliers.**

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**True**

If the sample data are normally distributed then we would expect the range between the mean-1.96*SD and the mean+1.96*SD to capture 95% of observations in the sample. If the sample is representative of the population, then this reference range can be a useful guide for comparing an individual's value with respect to other people in the population. This idea underpins growth charts and normal ranges for blood tests

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**True**

## DropDown Activity

The distribution of systolic blood pressure for a random sample of individuals extracted from a population of heavy smokers had a sample mean of 147mmHg and a standard deviation of 25mmHg

## True or False

A 95% reference range for SBP in smokers is found to be 97 to 197mmHg. How would you interpret this range?**Please indicate which of the following statements are acceptable.**

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**True**

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**False**

**This the reference range for a sample of smokers not the general population.**

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**True**

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**True**