Normal Distributions What is a Normal Distribution? Why are Many Variables Normally Distributed? Why are Many Variables Normally Distributed? How Are Normal.

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Presentation transcript:

Normal Distributions What is a Normal Distribution? Why are Many Variables Normally Distributed? Why are Many Variables Normally Distributed? How Are Normal Distributions Useful?

What is a Normal Distribution? A frequency distribution that has a symmetrical, bell shape with equal mean, median, and mode. Most scores are in the middle.

Why are Many Variables Normally Distributed? Many variables are assumed to be normally distributed. Why? Most variables are affected by many random factors. Random effects tend to balance out.

How are Normal Distributions Useful? Needed for inferential statistics. Find percentile ranks without knowing all the scores in the distribution. Determine probabilities.

Areas Under the Normal Distribution We can find a proportion of scores above or below a particular point in the normal distribution. This proportion can be interpreted as a percentage, or as a probability. We don’t need to know all the scores.