STATS Final Exam 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

Descriptive Statistics

methods of collecting and presenting data

Inferential Statistics

Determining intelligent guesses from populations

Statistic

a number that summarizes the sample data

sample

a subset of units in a population

Parameter

a number that summarizes all of the data of an entire population (average population)

Population

a collection of units that are being studied

Data

collection of numbers, characteristics, images, and other items that provide information about something.

Variable

a characteristic of each individual element of a population.

nominal categorical variable

gender, colors, blood types

ordinal categorical variable

letter grades, education levels, spice levels, class status

discrete numerical variable

something that you can count and the number won’t progress. Ex: #of students in a class, # of dogs in house.

continuous numerical variable

any real numbers between two whole numbers. Ex: peoples height, temperature, age

How do you know if a study’s results can be generalized to a targeted population?

If the sample is randomly selected and representative of the entire population

Which type study can make inferences?

• experimental

• observational

experimental

stratified sampling

population is divided into non-overlapping subgroups (aka:stratum) that share similar characteristics

cluster sampling

dividing population into non-overlapping subgroups (aka:clusters). Perform a simple random sample then select subgroups.

random sampling

sample is selected randomly from a list with every individual of the population.

multistage sample

randomly select units from inside of a randomly selected cluster.

explanatory variable

cause

response variable

effect

blocking variable

groups experimental units with similar characteristics, so researchers can isolate the effect of the treatment and eliminate the influence of nuisance factors.

How do you calculate IQR?

Q3-Q1

How do you calculate max upper whisker

Q3+1.5xIQR

how do you calculate max lower whicker

Q1-1.5xIQR

what is the shape of the graph is the mean is less than the median?

left skew

what is the shape of the graph is the mean is greater than the median?

right skew

what does it mean to be mutually exclusive?

events that cannot happen at the same time

What is disjoint term also know as?

mutaully exclusive

What is non-disjoint events?

events that can happen at the same time.

how do you find A^c

P(A^c)=1-P(A)

why are mutually exclusive events dependent?

because the occurrence of one event directly affects the probability of the other event

what does x stand for in the calculator?

mean

what does Sx stand for in the calculator?

standard deviation

what does range of IQR equal?

Q1 to Q3

how do I determine if something is independent?

if it is the “cause” in the study

How do I determine if something is dependent?

if it is the “effect” in the study

how do you determine if probability distribution is valid?

if the total adds up to 1

how do I find (AorB)

=P(A)+P(B)-P(AandB)

how do I find (AandB)

=P(A)xP(B)

What does a X_diff mean?

mean difference

What does S_diff mean?

standard deviation difference

What is the purpose of paired data?

To find if the average difference is different than 0.

What’s a paired t-test?

uses one sample and compare different data within the same sample

What’s a two sample t-test?

uses two separate samples and compare data

What’s a z/t test?

Comparing means from two groups to see wether they are so far apart that the observed difference cannot reasonably be attributed to sampling variability.

What’s ANOVA?

how do you calculate degree of freedom (df)?

n-1

what does a one-tailed test measure?

greater or less than hypothesis, where the critical values are only on one side of the graph.

how does t* being larger than z* affect the graph?

the graph of t* will be wider because t* has a greater margin of error.

Can we be confident in our observation if the confidence level contains 0?

no

how do I determine if a outlier is an influential point?