Lovesky 320 Midterm

descriptive statistics

numerical data used to measure and describe characteristics of groups. Includes measures of central tendency and measures of variation.

inferential statistics

numerical data that allow one to generalize- to infer from sample data the probability of something being true of a population

independent variable

The experimental factor that is manipulated; the variable whose effect is being studied.

dependent variable

The outcome factor; the variable that may change in response to manipulations of the independent variable.

what does NOIR stand for

nominal, ordinal interval, ratio

nominal scale

measurement in which numbers are assigned to objects or classes of objects solely for the purpose of identification

nominal scale example

Male = 1, Female = 2

ordinal scale

a scale of measurement in which the measurement categories form a rank order along a continuum

ordinal scale example

rank individuals

ratio scale

a quantitative scale of measurement in which the numerals have equal intervals and the value of zero truly means "nothing"

ratio scale example

height, weight, age

interval scale

a scale of measurement in which the intervals between numbers on the scale are all equal in size no true zero

interval scale example

temperature, IQ

sample mean symbol

M

population mean symbol

μ (mu)

sample standard deviation symbol

lower case s

population standard deviation symbol

σ (sigma)

population size

N

sample size

n

variance

the square of the standard deviation

standard deviation

measure of variability for the average distance that scores deviate from their mean. (square root of the variance)

standard normal distribution

A normal distribution with a mean of 0 and a standard deviation of 1.

empirical rule

68-95-99.7

z score

the number of standard deviations that a particular value lies for the mean on a standard scale

z score formula

M-mu/o

standard error

reflects the variability that we would expect to find in the values of that statistic over repeated trials

standard error of the mean formula

standard deviation / square root of sample size

sampling distribution

a distribution of all possible sample means or variances that could be obtained in samples of a given size from the same population; tells us what values we might or might not expect to obtain for a particular statistic under a set of predefined conditions

difference between sampling distribution and standard deviation

Standard Deviation measures the variability or spread of individual data points in a single dataset.

Sampling Distribution describes the variability of a statistic (like the sample mean) across different samples drawn from a population.

sampling error

is the natural discrepancy, or the amount of error, between a sample statistic and its corresponding population parameter

step 1 hypothesis testing

State the null and alternative hypotheses

step 2 hypothesis testing

set the criteria for a decision

step 3 hypothesis testing

Compute the test statistic

step 4 hypothesis testing

to make a decision

type I error

Rejecting null hypothesis when it is true

type II error

failing to reject a false null hypothesis

decision to retain the null is incorrect

type II error

decision to reject the null is incorrect

type I error

null hypothesis

a statement or idea that can be falsified, or proved wrong

alternate hypothesis

A statement that is accepted if the sample data provide sufficient evidence that the null hypothesis is false.

The relationship between sample size (n) and standard error of the mean (SE)

inversely proportional, as the sample size increases, the standard error decreases.

if p value is smaller than alpha

reject the null hypothesis

if p value is larger than alpha

fail to reject the null

In a survey, respondents are asked to rate their satisfaction with a product on a scale from 1 (very dissatisfied) to 5 (very satisfied). What type of measurement scale is being used here?

ordinal

You are collecting data on people's clothing sizes: Small, Medium, and Large. What scale of measurement is being used?

ordinal

A researcher is studying the years in which people were born. The data consists of the birth years of different individuals. Which scale of measurement applies to this data?

interval

A car manufacturer categorizes their vehicles into three categories: economy, mid-range, and luxury. Which scale of measurement is being used?

ordinal

discrete variables

values that can be counted as whole numbers, or categorical

continous variables

can assume infinte number, decimals

sex male or female

discrete, qualitative, nominal

number of dreams recalled

discrete, quanitative, ratio

duration of drug abuse in years

continuous, quantitative, ratio.

ranking of favorite food

discrete, qualitative, ordinal

college sat scores

discrete, quantitative, interval

two sample t test

Compares the means of two independent groups to see if they are significantly different from each other.

what can a z score be turned into

original raw score of a dataset, or it can be used to find other useful values, such as percentiles or probabilities from a standard normal distribution.