STATS exam 2 flashcards

what are Z-scores ?

they indicate how many standard deviations value is away from the mean

What is the equation for Z-scores?

(x-u)/(standard deviation)

parameter mean

mean value of an entire group under the study (usually over periods of time)

parameter proportion

percentage of population that meets a certain criterion or test (usually whether or not questions)

how do you determine when you can reject H₀ ?

value must be less than the a

what are conditions for inference?

sample size must be greater than 30

what does H₀ stand for?

null value which states there is no difference between a hypothesized and estimated value.

What does H_A stand for?

alternative hypothesis which states that there is a difference between a hypothesized and estimated value.

how big should p have to be have a right skewed graph?

small or <50

how big should p have to be to be left skewed?

large >50

what must you do to the sample size to decrease the margin of error?

increase sample size

whats the Z* for 90%?

1.64

What’s the a for 90%?

0.10

What’s the z* for 95%?

1.96

what’s the a for 95%?

0.05

what’s the z* for 99%?

2.57

what’s the a for 99%?

0.01

what’s a type I error?

when someone fails to reject a true null hypothesis

What’s a type II error?

when someone fails to reject a false hypothesis

68% of population is how many SD’s from the mean?

1

95% of population is how many SD’s from the mean

2

99.7% of population is how many SD’s from the mean

3

how do you find exact successes in a binomial problem?

P(X=k)

How do you find probability “of at least one” in a binomial problem?

1-P(X=0)

what does p mean?

probability of the shaded area of the graph

What is p head ?

sample proportion

As sample size increases what does standard error do?

decreases

CLT requirements

At least 10 successes and 10 failures

sample size of at least 30

samples must be independent

If you have to assume ME, what value do you use?

0.5

what factors would make the confidence interval narrower?

higher sample size

lower confidence level

how do you know when data provides convicing evidence?

when the p value is less than the significance level

What is a test statistic ?

a number calculated from data, that gives the compatibility with a null hypothesis

what must the z-score be to keep data under one standard deviation?

anything less than one

what must the z-score be for the data to be above average?

positive number

what must the z-score be for the data to be below average?

negative number

what is the equation of a test statistic?

z=(x-u)/SE