Probability and distributions

Question 1

what is a Symmetrical Distribution

Answer 1

When the distribution is reasonably symmetrical,

Bell shaped in a graph, expect about 95% of the observations to lie within 2 SD of the mean

Question 2

what is a skewed dis

Answer 2

when a histograme shows a lack of symmentry
positive skewed more common then negative
think of a graph that has a tail of data with a pack at one side

Question 3

if the data is symetircal what measures should you use

Answer 3

mean and SD

Question 4

if data is skewed what measures should you use

Answer 4

median and inter quartile range is more appropriate

Question 5

what do All probabilities lie between

Answer 5

0-1

Question 6

if the pro is 0 will the outcome ever happen

Answer 6

never can happen

Question 7

if the pro is 1 will the outcome happen

Answer 7

will definitely happen the probability is 1

Question 8

equation for addition rule

Answer 8

used when two outcomes A and B are mutually exclusive (I.e. when A occurs B cannot occur)

P(A or B) = P(A) + P(B)

Question 9

Multipulcation rule

Answer 9

Suppose two outcomes A and B are independent of each other (i.e. knowing the outcome of one experiment tells us nothing about the other experiment)

P(A and B) = P(A) x P(B)

Question 10

does all the observations in a normally distrbuted table fall under the curve

Answer 10

yes- area under the curve adds up to 1- it is called Probability Distribution

Question 11

in a normal dis do the mean and medium coincide

Answer 11

yes

Question 12

how many observations will lie outsode of 1SD from the mean

Answer 12

32%- 16 on each tail

Question 13

how many observations lie outside 2SD of the mean

Answer 13

5-2.5 on each tail

Question 14

how do you calculate the Z

Answer 14

(mean-number you are looking for-eg above 160 measures so 160 would be used)/ SD

Question 15

what is the use of the Z value

Answer 15

look on normal dis table which gives you the prob of being outside the range od the mean-