stats ch. 1
convenience sampling
"convenient" to select
population vs sample:
-WHOLE group -groupe we WANT To Know about -characteristics are called PARAMETERS -parameters are generally UNKNOWN -paramaters are FIXED -PART of the group -group we DO KNOW about -characteristics are called STATISTICS -statistics are always KNOWN -statistics CHANGE with the sample
EXAMPLE: the number on the uniform of a football player qualitatitve or quantitative? discrete, continuous, neither? what data?
-qualitatitve -neither -nominal
1.2 practice problem: a new feature on a CD player did not work properly. The manufacturer wanted to know if this caused users any problems. The users were asked to select one of the categories given below: 1-4 qualitative or quantitative? discrete or continuous or neither? what is the highest level of measurement of data?
-qualitative -neither -ordinal
1.2 practice problem: birth years of each person in your family qualitative or quantitative? discrete or continuous or neither? level of data?
-quantitative -discrete -interval
EXAMPLE: the IQ scores of students at the local college: qualitative or quantitative? discrete, continuous, neither? what data measurement?
-quantitative -discrete -interval
population
a particular group of interest -ex: the heights of all the okra plants at Mr. Lonardo's greenhouse
descriptive statistics
a science, gathers sorts, summarizes, and displays the data -ex: the avg. number of hours students in your stats class studies per week is 3.9 -ex: the avg. price of a car at the new car dealership in town is $28,600
inferential statistics
a science, involves using descriptive statistics to estimate population parameters -ex: a recent poll of 1420 home owners in Pennsylvania showed that the avg. price of a house in the US is $264,00
census
a study in which data are obtained from every member of the population
sample
a subset of the population from which data are collected
discrete data
can take on only particular values and cannot take on the values in between, usually COUNTS ex: the number of pets is discrete because you can have either 2 or 3 but not 2.75 ex: the numbers of people in each statistics class at your school
qualitative data
categorical data, consist of labels or descriptions of traits of the sample. NEITHER discrete or continuous ex: favorite foods, hometowns, eye colors, identification numbers ex: bank account numbers
cross-sectional study
characterized by data that are collected at a single point in time ex: a gastroenterologist surveys 130 of his patients six months after having gastric bypass surgery to determine the avg. amount of weight loss
systematic sample
chosen by selecting every nth member of the population ex: the quality control department at a cereal manufacturer measures the weight of every 10th box off the assembly
quantitative data
counts or measurements, therefore are numerical ex: test scores, avg. amounts of rainfall, weights ex: class sizes of various sections of college algebra at university ex: boiling points in degrees celsius for various substances
longitudinal study
data are gathered by following a particular group over a period of time ex: a group of 220 patients is followed for 15 years in order to determine the long term health effects resulting from gastric bypass surgery
parameter
numerical description of a population characteristic
sample statistic
numerical descriptions of sample characteristics -ex: a recent poll of 3810 students showed that the average number of hours a college student studies per week is 10.1
observational study
observes data that already exists ex: you want to determine the avg. age of college students across the nation
non sampling error
occurs from sources other than the construction of the sample ex: might be as simple as a typo in the data set, which is also known as a processing error
researcher bias
occurs when a researcher influences the results of a study
response bias
occurs when a researchers behavior causes a participant to alter his or her response or when a participant gives an inaccurate response ex: the wording of survey questions a researcher has given to participants
sampling bias
occurs when the sample chosen does not accurately represent the population being studied
nonresponse bias
occurs when there is a lack of participation in a self selected sample from certain segments of a population, when a person refuses to participate in a survey, or when a respondent omits questions when answering a survey
participation bias
occurs when there is a problem with either the participation or lack thereof of those chose for the study
random sample
on in which every member of the population has an equal chance of being selected ex: drawing names from a hat
cluster sample
one chosen by diving the population into groups, that are each similar to the entire population ex: a random number generator is used to choose fifty zip codes. Then a quality assurance analyst collects data from each person in these zip codes
stratified sample
one in which members of the population are divided into two or more subgroups, called strata, that share similar characteristics like age, gender, or ethnicity ex: a pollster surveys 50 people in each of a senators 12 voting precincts ex: a market researcher chooses 10 people at random from each class
dropouts
participants who begin a study but fail to complete it
nonadherents
participants who remain in the study until the end but stray from the directions they were given ex: a subject who finished the study but did not follow the directions they were given
participants
people being studied in an experiment
subjects
people or things being studied in an experiment
treatment
some condition that is applied to a group of subjects in an experiment
stratified vs cluster
strat= FEW members of EACH group clust= EACH member of a FEW groups
data
the counts, measurements, or observations gathered about a specific variable in a population in order to study it
statistics
the science of gathering, describing, and analyzing data OR the actual numerical descriptions of sample data
single blind
the subjects do not know if they are in the control group or the treatment group
explanatory variable
the variable in an experiment that causes the change in the response variable
response variable
the variable in an experiment that responds to the treatment
variable
value or characteristic that changes among members of the population
meta-analysis
when a study compiles information from previous studies, seeks to identify patterns across many studies on similar topics ex: oceanographers study research on tsunamis dating from 1900 to 200 to determine their effects on the ocean floor
cofounding variables
when researchers directly assign participants to the various groups they are controlling this. the factors other than the treatment that cause an effect on the groups ex: when comparing the test results of two groups of employees, confounding variables might include how long they have been at the company and what department they work in
treatment group
group of subjects to which the treatment is applied
representative sample
has the same relevant characteristics as the population and does not favor one group from the population over another
EXAMPLE: results sometimes produce flawed conclusions which can be a form of:
bias
ratio level
QUANTITATIVE, can be ordered with meaningful differences, and the zero point indicates the absence of something. this level we can add or subtract data values, we can also multiply or divide ex: consider the ages in whole years of US presidents when they were inaugurated
interval level
QUANTITATIVE, can be ordered, but the interval level is distinguished because differences between data entries are meaningful ex: the birth years of your classmates are collected
institutional review board (IRB)
a group of people who review the design of a study to make sure that it is appropriate and that no unnecessary harm will come to the subject involved
continuous data
can take on any value in a given range of numbers, usually MEASUREMENTS such as length and weight ex: heights of men entering the US Marine Corps
control group
does not receive treatment
sampling error
error in a study resulting from the way the sample was chosen
processing errors
errors that occur simply from the data being processed, such as typos when data are being entered
simple random sample
every sample from the population has an equal chance of being chosen ex: a market researcher gathers data from fifty stores by assigning each store an ID and selecting ID's using a random number generator
bias
favoring of a certain outcome in a study ex: favoritism, partiality, and preconceived notions
experiment
generates data to help identify cause-and-effect relationships ex: researchers wish to determine if flu shots actually help prevent severe cases of the flu
placebo
identical to the actual treatment but contains no intrinsic beneficial elements
informed consent
involves completely disclosing to participants the goals and procedures involved in a study and obtaining their agreement to participate
case study
looks at multiple variables that affect a single event ex: meteorologists study the Indian Ocean tsunami of December 2004 to try to identify warning signs ex: a produce manager inspects 10 ears of corn off a truck before purchasing the load
ordinal level
measurement is QUALITATIVE, can be arranged in a meaningful order, such as ranking or ordered rating, but calculations such as addition or division do not make sense ex: the seat numbers on your concert tickets, such as A23 and A24
nominal level
measurement is QUALITATIVE, consisting of labels or names ex: the genres of the music performed at the 2013 Grammys
double blind
neither the subjects nor the people interacting with the subjects such as doctors or nurses would know to which group each belongs
MEMORY BOOSTER FOR LEVELS:
nominal= names ordinal= order interval= 0 is a placeholder ratio= 0 means the absence of something QUALITATIVE DATA natural order? nominal= no natural order? ordinal= yes QUANTITATIVE DATA meaningful 0? interval= no meaningful 0? ratio= yes
