normam distribution Flashcards
1
Q
characteristics of normal distributions
A
- variable has to be continuous
- for a continuous variable, the area under the probability graph has to be 1
(so to find P(170<X<190>), use integration to find the area between these values) - y axis is the probability density
2
Q
the middle of the normal distribution curve is
A
the mean
3
Q
the larger the variance,
A
the wider the curve
4
Q
normal distribution format
A
X ~ N (mew, variance) (o^2)
5
Q
A
6
Q
the curve has
A
points of inflection one standard deviation away from the mean
(where the curve changes from concave to convex)
7
Q
the normal distribution is
A
symmetrical, mean = mode = median
8
Q
68-95-99.7 rule
A
- 68% of data is within one standard deviation of the mean
- 95% of data is within two standard deviations of the mean
- 99.7% of data is within three standard deviations of the mean
- for practical purposes, we consider all data to lie within mew + or - 5(variance)
9
Q
what is the z value
A
the number of standard deviations above the mean
10
Q
how to find z value
A
(X - mean) / standard deviation
11
Q
what is the standard normal distribution
A
X ~N (0,1^2)
mean = 0
sd = 1
12
Q
P(a<Z<b) is the same as
A
P(z<b) - p(z<a)
