QA 233 La Tech Test 1 Freling

chapter 1

the scales of measurement and introduction

what are the main scales of measurement?

nominal, ordinal, interval, and ratio

what is nominal?

categorical data, which can be coded numerically in to a dataset

what is ordinal?

nominal & order of rank in data is meaningful

what is interval?

ordinal & interval between values is expressed in terms of a fixed unit of measure (always numeric)

what is ratio?

interval properties & ratio of two values is meaningful (always numeric). zero means absence

what units of measure in qualitative data?

nominal & ordinal

what units of measure in quantitative?

interval & ratio

what is cross-sectional data?

data collected at the same or approximately the same point in time

what is time series data?

data collected over several time periods

what are the 2 types of data sources?

observational & experimental

what is observational?

data acquired by observing what is occurring in a particular setting and recording variables of interest (surveys, opinion polls)

what is experimental?

data collected under controlled conditions. variation in other variables is controlled, in order to yield interferences about the imp​act on variables of interest

what are descriptive statistics?

data that is summarized and presented in a form that is easy for the audience to understand (tables, graphs, numbers)

what is a statistical interface?

the application of statical processes to data collected from a sample to make estimates and test hypotheses about the characteristics of a population

what is a population?

set of all elements of interest in a particular study (greek letters are used to denote)

what is a census?

used to collect information from the entire population

what is a sample?

a subset of population

what is a sample survey?

used to collect data from a sample of the population

what is analytics?

the scientific process of transforming data into insight for making better decisions

what are descriptive analytics?

describe what has happened in the past

what are predictive analytics?

the use of analytical techniques that use models constructed from past data to predict the future or to assess the impact of one variable on another

chapter 2

what are the 2 methods for summarizing categorical data?

tabular & graphical

what is tabular data summarization?

frequency distribution, relative frequency distribution, and percentage frequency distribution

what is graphical data summarization?

bar chart & pie chart

what is a frequency distribution?

a tabular summary of data showing the number (frequency) fo observations in each of several unique categories or classes

what is relative frequency?

fraction or proportion of the total number of data items belonging to a class

relative frequency of a class = frequency of the class / n

what is n?

the sample

what is percent frequency?

relative frequency multiplied by 100

percent frequency = relative frequency * 100

what is percent frequency distribution?

tabular summary of a set of data showing the percent frequency for each class

how do you display frequency for categorical data?

bar chart & pie chart

how do you display frequency for quantitative data?

histogram, dot plot, and stem & leaf

what is a cumulative frequency distribution?

shows the number of data items with values less than or equal to the upper-class limit of each class

what is cumulative relative (percent) frequency distribution?

shows the proportion (percentage) of data items with values less than or equal to the upper limit of each class

what is a histogram?

similar to a bar chart, but no natural separation between classes in a histogram

what are the 3 main histogram distributions?

symmetric, left skewed, and right skewed

what is a dot plot?

quick way to manually create a histogram

what is a stem and leaf?

shows the shape of distribution of data and rank order at the same time

what is crosstabulation?

a tabular summary of data for two variables (can be the same type or one of each ex. categorical & quantitative)

how can you summarize 1 categorical and 1 quantitative crosstabulation?

side-by-side bar chart & stacked bar chart

how can you summarize a 2 quantitative cross tabulation?

scatter diagram

what is the greek letter for population mean?

looks like a u

what is the greek letter for population variance?

looks like an o^2

what is the greek letter for standard deviation?

looks like an o

what is the symbol for sample mean?

x

what is the symbol for sample variance?

what is the symbol for sample standard deviation?

s

what are the measures of location?

mean, median, mode, weighted mean, geometric mean, percentile, and quartile

what is the mean?

the average value (xbar or weird you)

sum of samples/ number of samples

what is the median

the middle value of a set of values arranged in ascending order

what is the mode?

the value that occurs most frequently in a set of values

what is weighted mean?

mean value calculated by giving each value a weight according to its importance (GPA, average stock price)

sum of sample * weight / total weight

what is geometric mean?

the nth root of the product of n values

n square root x1x2... xn

what is percentile?

provides information about how data is spread over the maximium and minimum values

what are quartiles?

specific percentiles that divide the data set into 4 parts

what are the measures of variability?

range, interquartile range (IQR), variance, standard deviation, and coefficient of variation

what is range?

the difference between the largest and smallest values in a data set

what is interquartile range (IQR)

the measure of variability between the first and third quartile i.e the middle 50%

what is variance

the measure of variability based on the squared deviation of the mean

population variance =

sum of (xi - xbar)^2 / N

standard deviation

the square root of the variance

coefficient of variation

a measure of how large the standard deviation is relative to the mean

standard deviation / mean * 100

what is skewness?

a measure of how much the distribution of values in a data set deviate from symmetric (negative skewness, positive skewness, or 0 skewness)

what is relative location?

how much the values of a data set deviate from the mean

what are z-scores (standardized value)?

the number of standard deviations a value is away from the mean

what is the empirical rule?

applies to data values that exhibit a symmetric bell-shaped distribution - helps determine outliers

what is covariance?

the measure of the linear relationship between two variables

sample covariance =

the sum of (xi - xbar) * (yi - ybar) / (n - 1)

what is the pearson product women correlation?

measure of the linear relationship between two variables

sampel rxy =

sample covariance / (std.dev of x) * (std.dev of y)

population pxy =

population varience xy / population varience x * population varience y

what are combinations?

the order of the selection is not important when selecting from a population

what are permutations?

the order of the selection is important when selecting from a population

what are the 3 ways of assigning probability?

classical method, relative frequency method, and subjective method

what is the classical method?

assigning probabilities based on the assumption of equally likely outcomes

rolling a die

what is the relative frequency method?

assigning probabilities based on experimentation or historical data

waiting time at the doctor's office

what is the subjective method?

assigning probabilities based on judgment, using experience and intuition

tom and judy make an offer to purchase a house

judy says .8 for accepted & .2 for not

tom says .6 for accepted & .4 for not

what is an event?

collection of sample points

what is the probability of any even?

equal to the sum of the probabilities of the sample points in the event

what are the basic probability relationships?

complement, union, intersection, mutually exclusive

what is a complementing relationship of events?

event A is defined to be the event consisting of all sample points that are not in A

what is the addition law?

compute the probability of event A, or B, or both A and B occurring

P(AuB) = P(A) + P(B) - P(AnB)

what is a union of two events?

event containing all sample points that are in A or B or both (AuB)

what is the intersecting of two events?

set of all sample points that are in both A and B (AnB)

what is the mutual exclusivity of 2 events?

the events have no sample points in common, and when one occurs the other cannot

what is conditional probability?

the probability of an event given that another event has occurred

P(A|B) = A given B

P(A|B) = P(AnB)/P(B)

what is the multiplication law?

a way to compute the probability of the intersection of two events

P(AnB) = P(B)P(A|B)

what is an independent event?

the probability of event ! is not changed by the existence of event B

what is babes theorem?

revising prior probabilities

what is a posterior probability?

what is the tabular approach?