STAT 2625 | Exam 1

What is Statistics?

Statistics is the science of understanding data and of making decisions in the face of "variability" and "uncertainty".

what is a varible that contains only two categories of outcomes called?

a binary variabale

what is a variable?

a characteristic of interest for the individual which take on different values in different individuals

what is a pie chart/graph?

a circle that is divided into sections (wedges) according to percentage of frequencies in each category of the distribution

why is convenient sampling not reccomended?

a convenient sampling approach is unable to obtain a representative sample

what is a stem and leaf plot?

a data plot that uses part of the data value as the stem and the other part as the leaf in order to form groups and classes

what is a completely randomized experimental design?

a design of experiment in which all the experimental units are allocated at random among all the treatments

what is bimodal shape?

a distribution that has two peaks of the same height

what is a scatter plot?

a graph of ordered pairs of data values that is used to determine of a relationship exists between two variables

what is a frequency polygon?

a graph that displays data by using lines that connect points plotted for the frequencies at the midpoints of the classes

what is a cumulative frequency graph?

a graph that represents the cumulative frequency for classes in a frequency distribution

what is an ogive?

a graph that represents the cumulative frequency for classes in a frequency distribution

what is a relative frequency graph?

a graph that uses the relative frequencies of each class

what is a pareto chart?

a graph used to represent a frequency distribution for a categorical variable; the frequencies are displayed by the heights of vertical bars which are arranged from highest to lowest

what is a frequency distribution?

a listing of classes and their frequencies

what is a relative frequency distribution?

a listing of classes and their relative frequencies

what is a parameter?

a numerical summary of a population

what is a statistic?

a numerical summary of a sample

what is stratified random sampling?

a population is classified into at least two strata and then a sample is drawn from all strata

wat is cluster sampling?

a population is divided into sections, all members of a few ( but not all) of the sections are randomly selected and a sample is drawn from the selections

what is a binary variable?

a qualitative variable that contains only two categories of outcomes

what is a convenient sample?

a sample drawn from results that are already available or using data that is convenient to obtain

what is systematic sampling?

a sample is obtained by selecting every k-th member of the population where k is a counting number

what is simple random sampling?

a sample obtained from a population in such a manner that all samples from the size have equal likelihood of being selected

what is symmetric (bell) shape?

a single peak that tapers off at either end; roughly the same on both sides of a line running through the center

what is a dot plot?

a statistical graph in which each data or data value has been plotted as a point above the horizontal axis

what is a quantitative variable?

a variable that can be measured

what is a discrete variable?

a variable that has a countable number of possible values

what is a continuous variable?

a variable that has an uncountable number of possible values

what is univariate anaysis?

an analysis that involves only a single variable

what is a bivariate analysis?

an analysis that involves two variables

what is a sample?

any subset of individuals from the population

what is the hawthrone effect?

bias from the fact that subjects know that they are participated in the experiment

in a frequency polygon, how is frequency represented?

by the heights of points

in what ways are categorical data grouped and displayed?

categorical frequency tables and charts, bar graphs, and pie charts

what are classes?

categories for grouping data

in a frequency distribution, what values are used on the x and y axes?

class midpoints are used on the x axis and frequencies are used on the y axis

what is an experimental study?

conditions to which subject are exposed and controlled by the investigator (manipulated treatments are used to see their effect on other variables)

what is an observational study?

conditions to which subject are exposed and uncontrolled by the investigator (no attempt is made to control or influence the variable of interest)

what are nominal level measurements?

consists of labels, names or categories

what is used on the x and y axes on a cumulative frequency (ogive) graph?

cumulative frequency is used on the y axis and class boundaries are used on the x axis

what is a time series graph?

data represented over a specific period of time

what are ordinal level measurements?

data where the order or rank is meaningful

what are ratio level measurements?

data where the ratio of two data is meaningful

what does data production entail?

design studies and data collection

what are the two types of quantitative variables?

discrete and continuous variables

what two ideas encompass the purpose of inferential statistics?

estimation and hypothesis testing

what values are used on the x and y axes on a cumulative frequency graph?

midpoints are used on the x axis and relative frequency is used on the y axis

what are the 4 kinds of measurements?

nominal, ordinal, interval, and ratio

what are interval level measurements?

numerical data where the arithmetic operations are meaningful

what are the two types of statistical studies?

observational and experimental studies

what are outliers?

observations that stand out from the rest of the data set

what should be observed in a histogram?

outliers, the center, the spread, and the shape

what are the two variable types?

quantitative and qualitative variables

in what ways is data sourced?

routinely kept records, surveys, designed experiments, and external sources (like the internet, public or private organizations)

what is sample standard deviation?

s measures the spread around the mean, the large s is, the more spread out the data are; if s = 0, then all the observations must be equal; s is strongly influenced by outliers

what is the difference between sample mean and population mean?

sample mean is the average values of data obtained from a sample, while population mean is the average of data obtained from an a=entire population

what are the 5 distribution shapes?

symmetric, skewed right, skewed left, bimodal, and uniform

what is the midrange?

the average of the lowest and the highest values in the data set

what is the mean?

the average value of the data?

what is a modal class?

the class in a frequency distribution with the highest frequency

what is a population?

the collection of all individuals of interest in a statistical study

what is the median of a data set?

the data value exactly in the middle of its ordered list if the number of pieces in the data is odd; the mean of the two middle data values in its ordered list of the number of pieces of data are even.

what is the center of the data?

the data values that occur in the middle of a data set

what is the range?

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

what is the class width?

the difference between the lower class limit of the given classes and the lower class limit of the next higher class

what is shape?

the distribution pattern; the skewness, symmetry, and uniformity of the data

what is data?

the facts and figures that are collected and analyzed in a statistical study

what is on the x and y axes in a histogram?

the frequencies of each class are plotted on the y axis and the class boundaries (class limits) are plotted on the y axis

what is the upper class limit?

the largest value that can go in a class

what is the weighted mean?

the mean of a data set in which not all values are equally represented

what is variance and standard deviation?

the measure o f the spread of the data around the center of the data

what is the class midpoint (class mark)?

the midpoint of a class

what is the mode of a data set?

the mode of a data set is the observation that occurs most frequently; the class with the highest frequency

what is frequency and class frequency?

the number of data values in a class

what are possible problems that arrise from completely randomized design experiments?

the placebo effect and the Hawthrone effect

What is Chebyshev's Theorem?

the proportion of values from a data set that will fall within k standard deviations of the mean will be at least 1 - 1/k^2, where k is a number greater than 1

what is the formula for finding class width?

the range of the data divided by the number of classes

what is a spread?

the range; the extent of the data; how far the values are from each other

what is relative frequency?

the ratio of the frequency of a class to the total number of pieces of data

what is the lower class limit?

the smallest value that can go in a class

what is the coefficient of variation?

the standard deviation expressed as a percentage of the mean. it is a unit free measure of dispersion and provides a measurement for comparing relative variability of data sets from different scales

what are the guidelines of grouping data for quantitative variables?

there should be between five and twenty classes, each piece of data must belong to one class (mutually exclusive), and all classes should have the same width (when feasible)

what are the uses of mean and standard deviation?

they describe a distribution and help you understand the center and the spread of the distribution

what is the purpose of sampling techniques?

to obtain a representative sample

what are the two basic types of analyses in introductory statistics?

univariate analysis and bivariate analysis

what two areas are measured through statistics?

variability and incertainty

what is a confounding effect?

variables are said to be confounded when their effects on the outcome cannot be distinguished from each other, whether they are part of the study or not

what is skewed left or negatively skewed?

when data values are clustered to the right an taper off to the left

what is skewed right or positively skewed?

when the peak of a distribution is to the left and the data values taper off to the right

what is the notation used for sample mean?

x-bar

what is the notation used for population mean?

μ

what is the formula to find the number of classes suitable for a distribution?

1 + 3.3log(n), where n is the sample size

statistics is a field of study concerned with what three areas?

1) data collection, 2) organization, summarization, examination and providing an overview of the general features of data, 3) and the drawing of inferences about a body of data (population) based on the properties of a part of the data (sample) observed.

what are the three areas of statistics?

1) sampling 2) descriptive statistics 3) inferential statistics

what is uniform shape?

flat or rectangular in shape

what information is collected from a scatter plot?

form (straight line or curve relation), direction (positive or negative relation), strength (strong or weak relation) and outliers

what is descriptive statistics?

grouping tables an graphical summary; numerical summary

what are display distributions for continuous or quantitative variables?

histograms, frequency polygons, ogives, and relative frequency graphs

what are "individuals" in terms of an experimental study?

individuals are subjects, experimental units, and or the entities on which data are collected