PSY2811 Exam 2

Descriptive Statistics

Used to organize, screen for issues, summarize main details

Inferential Statistics

Use data from sample to make conclusions about overall population

Population

total collection of things we are seeking info about

(“mu”/unknown) population parameters

any summary of numbers that describes characteristics of entire population

Does it matter what graph you use for differential statistics?

Yes

Bigger sample size = ________________ confidence interval

smaller

Two major things in hypothesis testing

Falsification, testing your prediction against the alternative possibility

Is this worded right: “I reject the null”

yes

Is this worded right: “The null is wrong”

NO- you can not definitely prove right and wrong

Is this worded right: “I failed to reject the null”

yes

SEST

as we get older we are more motivated to regulate negitive emotions, which leads to a better wellbeing

What does a Frequency distribution table help with?

organize data, detect weird values, orders raw data

What does a frequency distribution table use to organize data?

Bins

What are the rules of the bins?

exclusive, equal sized, exhaustive

What is a cumulative frequency table and what is it used for?

Accumulated scores across bins. Useful for: counting scores below or above threshold value.

Histogram

Normal

Positively Skewed

Negatively Skewed

What is central tendency (3)?

Mode, Median, Mean

Central Tendency

these measures summarize the middle or most typical values for a varible

What two factors guide what central tendency we use?

1) level of measurement (nominal, ordinal etc)

2) Shape of distribution (normal, skewed)

Mode

The most common values of varibles

Nominal variables can only use what type of central tendency?

Mode

Median defination

middle value of distribution (data in order)

What central tendency should you use for a nominal value?

mode

What is the best central tendency to use if your distribution is skewed?

Median- it does not include all the data

Mean definition

arithmetic average of all variables in data

What should you use when the data is simetrical?

Mean- it is influenced with outliers

T or F: The mean is skewed by the tail

true

Variability

causes central tendencies to vary

Where does varability come from?

We are human, everyone is diffrent

Participant variability happens in four main ways….

Between subject, within day and subject, random errors, systematic

What 3 Participant varabilitys can we live with?

Between subject, within a given subject/day to day, random errors

What is the one participant validity that we have to fix?

Systematic- being constantly off set from the true score

How do we quantify variability?

With range, Interquartile Range, Box and wisker plot

What is the Range?

The diffrence between the minimun and maximun

What is interquartile range?

the middle 50% of the data set (between Q1 and Q3)

Greater deviation = ____________ spread of scores

greater

mean absolute deviation

The average distance each score is from mean

sum of squares

take each deviation from the mean

z-score = 0

equal to the mean

z-score<0

zscore is less than mean

zscore>0

greater than the mean

what is Z-score

shows how many SD a score is above or below the mean of its distribution

TorF: z-scores have a unit

FALSE- they are unit free, standardized

Column A shows what

Z-scores

Column B has what

prortion os data between mean and z-score

Column C has what

proportion of data beyond z-score

P-value

The probability that you would have seen this data of NULL was true

Power

the probability of correctly rejecting the null hypothesis

Lower alpha

lower power

lower alpha, you reduce your power makes it __________ to reject the null

harder

Type 1 error

false positive

Type 2 error

false negative

Sum of squares

Sum of squares

Population Deviation

Sample Devation

population SD

Sample SD

z-score