Chapter One- Introduction to Statistics Flashcards
What is data?
Data are collections of observations, such as measurements, genders, or survey responses.
What is datum?
A single data value
What is statistics?
Statistics is the science of planning studies and experiments; obtaining data; and then organizing, summarizing, presenting, analyzing, and interpreting those date and then drawing conclusions based on them.
What is a population?
A population is the complete collection of ALL measurements or data that are being considered.
What is a census?
A census is the collection of data from EVERY member of the population.
What is a sample?
A sample is a sub-collection of members from a population.
What is a parameter?
A parameter is a numerical measurement describing some characteristic of a population.
What is a statistic?
A statistic is a numerical measurement describing some characteristic of a sample.
What does Quantitative data consist of?
Quantitative data consist of numbers representing counts or measurements.
What does Categorical data consist of?
Categorical data consist of names or labels that are NOT numbers representing counts or measurements.
When does Discrete Data result?
Discrete Data result when the data values are quantitative and the number of values is finite or “countable”. (If there are infinitely many values, the collection of values is countable if it is possible to count them individually, such as the number of tosses of a coin before getting tails.
When does Continuous Data result?
Continuous Data result from infinitely many possible quantitative values, where the collection of values is not countable. (That is, it is impossible to count the individual items because at least some of them are on a continuous scale, such as the lengths from 0cm to 12cm.)
Define “ Nominal Level of Measurement”.
The Nominal Level of Measurement is characterized by data that consist of names, labels, or categories only. The data cannot be arranged in an ordering scheme (such as low to high).
Define “ Ordinal Level of Measurement”.
Data are at the Ordinal Level of Measurement if they can be arranged in some order, but differences (obtained by subtraction) between data values either cannot be determined or are meaningless.
Define “Interval Level of Measurement”.
Data are at the Interval Level of Measurement if they can be arranged in order, and differences between data values can be found and are meaningful. Data at this level do not have a natural zero starting point at which none of the quantity is present.
Define “ Ratio Level of Measurement”.
Data are at the Ratio Level of Measurement if they can be arranged in order, differences can be found and are meaningful, and there is a natural zero starting point (where zero indicates that NONE of the quantity is present). For data at this level, difference and ratios are both meaningful.
Define “Observational Study”.
In an observational study, we observe and measure specific characteristics, but we don’t attempt to modify the subjects being studied.
Define “Experimental Study”
In an experiment, we apply some treatment and then proceed to observe its effects on the subjects, (subjects in experiments are called experimental units)
What is “random sampling”?
Random Sampling is when each member of the population has an equal chance of being selected. Computers are often used to generate random telephone numbers.
What is “simple random sampling”?
Simple Random Sampling is when a sample of N subjects is selected in such a way that every possible sample of the same size N has the same chance of being chosen.
What is “systematic sampling”?
Systematic Sampling is when you select a starting point, then select every kth (such as every 50th) element in the population.
What is “convenience sampling”?
Convenience sampling is when you use results that are easy to get.
What is “stratified sampling”?
Stratified sampling is when you subdivide the population into at least two different subgroups (or strata) so that subjects within the same subgroup share the same characteristics) such as gender or age bracket), then draw a sample from each subgroup.
What is “cluster sampling”?
Cluster sampling is when you divide the population into sections (or clusters), then randomly select some of those clusters, and then choose ALL members from those selected clusters.
In a cross sectional study, data…
In a cross sectional study, data are observed, measured, and collected at one point in time, not over a period of time.
In a retrospective (or case control) study data are collected from…
data are collected from a past time period by going back in time (through examination of records, interviews, and so on).
In a prospective (or longitudinal or cohort) study data are collected in…
data are collected in the future from groups that share common factors (such as groups area called cohorts).
Define “randomization”.
Randomization is used when subjects are assigned to different groups through a process of random selection.
Define “replication”
Replication is the repetition of an experiment on more than one subject.
Define “Blinding”
Blinding is in effect when the subject doesn’t know whether he or she is receiving a treatment or a placebo.
Define “placebo effect”
Placebo effect, occurs when an untreated subject reports an improvement in symptoms.
Define “double blind”
Double blind means that blinding occurred at two levels: the test subject does not know if they are given the drug or placebo and the doctors who give the drug also do not know if it is the drug or a placebo
Define “confounding”
Confounding occurs in an experiment when the investigators are not able to distinguish among the effects of different factors.
What experiment design is being used when we form a block of women and a block of men and within each block, randomly select subjects to be treated?
Randomized block design
What experiment design is being used when we use randomness to determine who gets the treatment and who gets the placebo?
Completely randomized experimental design
What experiment design is being used when we get measurements from the same subjects before and after some treatment?
Matched pairs design
When does a sampling error occur?
A sampling error occurs when the sample has been selected with a random method, but there is a discrepancy between a sample result and the true population result; such an error results from chance sample fluctuations.
A non sampling error is the result of?
Is the result of human error, including such factors as wrong data entries, computing errors, questions with biased wording, false data provided by respondents, forming biased conclusions, or applying statistical methods that are not appropriate for the circumstances.
A random sampling error is the result of?
Is the result of using a sampling method that is not random, such as using a convenience sample or voluntary response sample.
