Stats- test 1

What is the goal of statistics

to make inferences about populations using samples

Define statistics

the science of collecting, organizing, summarizing, and analyzing information to draw conclusions or answer questions

What is data

 the information gathered used to draw a conclusion

what are recorded characteristics referred to as

variables

What are the two encompassing variables

qualitative and quantitative

What are the types of quantitative variables

• discrete

• continuous

What is a discrete variable

a countable variable, a whole number

What is a continuous variable

an uncountable variable, a decimal

What is an explanatory variable

the independent variable, the variable that is purposefully changed

What is a response variable

the dependent variable, the variable that changes in response to the purposefully manipulated variable

Describe and observational study

a study that does not attempt to manipulate anything but rather observes the relationship between the response and explanatory variable

What kind of relationship can you claim with an observational study

association or correlation

Describe a designed experiment

A designed experiment is where a a researcher purposefully manipulated the explanatory variable and controls the rest of the other variables in order to determine the relationship between the response and explanatory variable

What relationship can you claim with a designed experiment

causal

What is the group of people being studied called

population

What is the smaller group being used to study the population referred to

sample

What should the sample size always be in relation to the population

it should always be smaller

What are all statistical methods based on the notion of what

randomness

What is the gold standard of sampling

simple random sample

What is simple random sampling

A sample of size n from o population of size N is obtained through simple random sampling if every possible sample of size n has an equally likely chance of occurring

What is stratified sampling

 separate the population into the non-overlapping groups called strata (the individuals in each group should be as similar as possible). Then choose a random individual from each stratum for your population

What is cluster sampling

make random clusters and pick a cluster, and that is your sample

What is systematic sampling

selecting every kth individual from the population. The first individual selected is a number between 1-k (like every 5th person is chosen)

What is convenience sampling

getting a sample based on convenience to the researcher, only gets to claim association

What is a lurking variable

a variable that was unaccounted for that could influence the results of a study

What is a confounding variable

a variable that cannot be separated from the explanatory variable and therefore cannot determine a true causal relationship.

When is a variable at the nominal level of measurement

if the variable’s values allow for categorizing, labeling, or naming but not ranking in a specific oreer

When is a variable at the ordinal level of measurement

when the variable’s values allow for both naming/categorizing/labeling (like the nominal level) and ranking in a specific order

When is a variable at the interval level of measurement

When the variable’s values allow for labeling/labeling/categorizing and ranking in a specific order (ordinal) and the differences in the values hold meaning. Addition and subtraction can be performed on this variable

When is a variable at the ratio level of measurement

When a variable’s values allow for naming/labeling/categorizing, being ranked in a specific order, the differences in values of the categories having meaning, substraction and addition can be done to the values (interval), and the ratios of the values have meaning, multiplication and division can be done one these values

Describe a cross sectional study

an observational study that collects information a specific point in time/ short period of time

Describe a case control study

a retrospective study where the researcher looks back in time by asking individuals to recall specifics or looking at pre-existing records

Describe a cohort study

First the study identifies a group of individuals to participate in the study and those individuals are observed over a long period of time and their characteristics recorded- making these studies prospective

What does this variable represent?

population arithmetic mean

What is a parameter in statistics

something that describes the entire population

What is a statistic in statistics

describes a sample set of data

Is u a parameter or a statistic

parameter

What does this symbol represent

the arithmetic mean of the sample

What does N represent?

the size of the population

What does n represent

the size of the sample

What does M represent

the median

When is a numerical summery of data resistant?

extreme observations (outliers) do not heavily affect the numerical summery

if the mean is smaller than the median then the graph is

skewed left

if the mean is larger than the median then the graph is

skewed right

if the mean and median are roughly equal

graph is symmetric

what is dispersion

the degree to which the data are spread out

what does R represent

range

what does sigma represent

standard deviation of the mean

what is the variance of a variable

s²

what is the population variance

sigma²

What is the empirical rule

1. approx 68% of data will lie within 1 standard deviation of the mean (mew-1 sigma)

2. apporx 95% of the data will lie within 2 standard deviation of the mean (mew-2 sigma)

3. approx 99.7% of the data will lie within 3 standard deviation of the mean (mew- 3 sigma)

How do you find IQR

3 Q - 1 Q

What does IQ R tell us

spread of middle 50%

large IQR- middle values are more dispersed

small IQR- middle values closer together

What is s

sample standard deviation

how does sample standard deviation differ from population standard deviation

sample is divided by n-1 and population is divided by N

what does variance of a variable show

how spread out dad points are from the mean