U4L4

Question 1

Skewed and unimodal distributions

Answer 1

Skewed and unimodal distributions
A distribution which is not symmetric may be positively (tail pulled to right) or negatively (tail pulled to left) skewed.
Both distribution types are considered to be unimodal (1 mode).
Hump in graph = mode

Question 2

Bimodal distributions

Answer 2

Bimodal distributions
When a distribution has two humps
Ex. adult shoe sizes see two spikes, one for female shoe sizes and one for male shoe sizes.

Question 3

The only way to find the probability

Answer 3

The only way to find the probability over a particular interval is to find the area under the probability densité over the interval we are investigating (the area under the curve for the interval).

Question 4

The normal distribution is

Answer 4

The normal distribution is symmetrical and unimodal. This gives a bell curve look and is considered to be normal.

When it is symmetrical the mean=mode=median

Smaller standard deviation = more narrow the hump is.

Question 5

A population that follows normal distribution can be completely described by its

Answer 5

A population that follows normal distribution can be completely described by its mean, μ, and standard deviation, σ.

Question 6

68 95 99.7 rule

Answer 6

68 95 99.7 rule - for any normal distribution, approximately:
68% of the data values of x will lie within the ranges μ-σ and μ+σ
95% of the data values of x will lie within the ranges 2μ-σ and 2μ+σ
99.7% of the data values of x will lie within the ranges 3μ-σ and 3μ+σ

The notation used to describe a normal distribution of the variable X is X~N(xbar,σ2).