Statistics (4)

Question 1

RIPS

Answer 1

Random / unpredictable event
Independent event
Proportional. Constant rate throughout the time interval.
Simotaneous (not).

Question 2

FIST

Answer 2

Fixed # of trials
Independent events
Same probability
Two outcomes only

Question 3

Inverse Poisson

Answer 3

Make x =0 and find the prob
Area = e to the -ve lambda
ln(a) = -lam lin(e)
ln(a) - -ve lam
lam = -ln(a)

Question 4

If binomial has
___ and ____

Answer 4

Multiply the 2 answers

Question 5

Different assumptions

Answer 5

Dependent/Independent
Environments
Picked from a random selection

Question 6

N.D with a min & pax percentage

Answer 6

Find the 2 z-scores
Use the z-score formula
Change it around
Use simotaneous on calc

Question 7

How to find the z-score?

Answer 7

Z = (x-m) / s.d
In inverse
Mean = 0, s.d = 1

Question 8

S.D of triangular

Answer 8

sqrt(a^2+b^2+c^2)+(ab)+(ac)+(bc)
/
18

Question 9

Mean of triangular

Answer 9

a + b + c / 3

Question 10

Mean of rectangular

Answer 10

a + b /2

Question 11

S.D of rectangular

Answer 11

1/sqrt12 x (b-a)

Question 12

If something happens to two people

Answer 12

Square the answer

Question 12

Does a N.D fit?

Answer 12

Symetrical
Bell-shaped
Continuous
Higher or lower than bounds shown
68% in 1, 95% in 2, 99.7% in 3

Question 13

Jusitfy/assumtions for any discrete distribution

Answer 13

That no value is lesser/greater than what is listed

Question 14

How to find if DRV are independent

Answer 14

VAR(x+y) = var(x) + var(y)

Question 15

At least 5/10 xxx are smaller than xxx in a triangular distribution

Answer 15

Use triangular first
Then use binomial

Question 16

Compare a normal distribution to another one

Answer 16

Talk about the mean and S.D
One mean is larger, by xx, meaning that it will produce more on average.
S.D is larger, meaning that it’s more consistent.
Part in the middle is one, parts on the edge is the other.

Question 17

Poisson or binomial occurs at least xxx in 5 different things. Calculate & assume

Answer 17

The answer to the power of 5.
We’re assuming it’s independent, but this may not be valid because…

Question 18

Given that something already happened, what’s the liklehood of another thing happening?

Answer 18

(p x>1) / p (x>2)
Given that … on the bottom.
If it’s less than, on the top do (y<x<z)

Question 19

In binomial/poisson: p(x>=6)

Answer 19

1 - P(x<=5)

Question 20

Calculate something OR something

Answer 20

Do the 2 and add them

Question 21

Compare the liklehood of events. How much more likely is a than b?

Answer 21

Divide the biggest answer by the smallest. What it equals to is how much more likely it is.

Question 22

The probability of two things both happening

Answer 22

Do the maths, then multiply their answers

Question 23

Binomial or poisson, there is an unknown n number of something, the prob of at least 1 being … is 0.9. What is n?

Answer 23

Find out the prob of 0, which is 1-p(x>=1).
What’s the probability that that thing isn’t?
Probability to the n = probability p(x=0)
Logs

Question 24

For triangular, why isn't the mean & median equal?

Answer 24

For mode to = median, 50% of ... would need to be greater than the median. Calculate, and see that this is not true.

Question 25

There are 2 outcomes for something, and they want to see if the outcomes are equal, and there's a table.

Answer 25

P=0.5, find the prob of the 2 of them and set them equal. If there's a small difference, say that there are only a few trials, and there is variation that is expected. There isn't sufficient evidence in this case.

Question 26

Binomial - n number of something, p(n>0) = x. Idk find n

Answer 26

Prob to the n = x Put n as zero to find x

Question 27

With DRV, are most results more than something?

Answer 27

Add the prob up of those which are greater. If over .5, then yes.

Question 28

What is the variance in DRV?

Answer 28

The SD squared

Question 29

Standard deviation/spread for binomial/poisson

Answer 29

It's given in formula sheet. Square root of (n x prob x (1-prob)

Question 30

In DRV, how to tell if the SD increased/decreased?

Answer 30

If the mode has decreased, and there is a more even spread