4 - Confidence And hypothesis

Question 0

What is Poisson distribution in terms of…
n
The variance in relation to the mean
Distribution

Answer 0

• N - numbers/counts in specified intervals
• Variance:mean - variance equal to mean. Mean typically close to 0. As mean increases it looks like flattened normal distribution
• distribution - approx randomly distributed

Question 1

What factors are needed to construct the confidence interval for either a sample or a population

Answer 1

Sample or population mean
Level of confidence (e.g. 95%)
Standard error of the sample mean OR standard deviation for a population

Question 2

What is a z score?

Answer 2

Number of standard deviations that a given observation is away from the population mean
Z = (x-mean)/standard deviation

Question 3

How do you calculate a t score?

Answer 3

T = (observed value - sample mean) / sample standard error

Question 4

P=0.95 (95.44%) is the probability that an observation within + or - of _____ x standard deviation.

Answer 4

1.96x standard deviation

Question 5

P=0.99 (___%) Is the probability that an observation is + or - ____x standard deviation

Answer 5

(99. 74%)

2. 58 x standard deviation

Question 6

What are the confidence limits?

Answer 6

Limits between which estimated parameters are likely to occur. Expressed as a confidence coefficient. Aways 2 numbers, not the range.

Question 7

What is the confidence interval?

Answer 7

Range of values between upper and lower limits, between which a sample is likely to fall.

Question 8

For a 95% confidence limit : upper and lower limits of confidence interval are given by:
Mean + or - (standard error x ____)
Where ____ is a critical number (t value)

Answer 8

1. 96

1. 96

Question 9

What does 95% confidence interval mean?

Answer 9

95 times out of 100, the sample mean will be within 95% confidence limits

Question 10

How do you calculate sample standard error?

Answer 10

Sample standard deviation / square root of sample number

Question 11

How would you calculate degrees of freedom?

Answer 11

N-1

Question 12

On a box plot, where are the extreme values in a positive skew? Where is the median?

Answer 12

Extreme to The right so the median is to the left.

Question 13

What is an alpha level?

Answer 13

Level of significance to reject the null hypothesis

Question 14

If p < p value for significance

Answer 14

Reject the null hypothesis - there is a difference!