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Test 1
MSIT chapter 2,3,4,5,7,8
47
Mathematics
Undergraduate 2
01/22/2015

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Term
Who
Definition
Rows.
The individual items for which we record several different measurements.
Term
What
Definition
Columns.
The measurements (variables) about these individual items.
Term
Individual cases
Definition
the who's/rows
Term
Variables
Definition
The measurements recorded about each individual item and are shown in the columns of the data table. They identify What has been measured for each item.
Term
Quantitative Variable
Definition
how much of something was measured, and tells us exactly how far apart 2 individual items are.
Ex: height, weight, salary, score, distance, time, GPA.
They have units.
Term
Categorical Variable
Definition
It is not possible to specify exactly how far apart 2 individuals are. Examples: gender, race, nationality, hair color, student ID, university major, phone number, zip code, Y/N
Term
Identifier
Definition
a unique identification assigned to each individual or item. This is listed in the first column of the data table. It could be a name or an alpha-numeric code.
Term
Time Series
Definition
Data that consist of the same item measured repeatedly over time.
Ex: daily stock prices for the past 10 years, GDP of the US for the past 30 years
Term
Cross-Sectional
Definition
Data that are measured at the same point in time.
ex: the GDP of all the European countries for 2013, or the closing price yesterday of all the stocks in the Nasdaq 100.
Term
Biased
Definition
Sampling methods that over- or underemphasize certain characteristics of the population. Differs systematically from the population it is trying to represent. A larger sample size does not correct the bias since the underlying method has a systematic problem.
Term
Census
Definition
A “sample” that includes the entire population. Attempting a census is often less accurate than a sample
Term
Population Parameter
Definition
the true, exact value in the population that we wish we knew. For instance: the true average salary of Terry alumni,
the true average hours per week worked by accountants, the true market share of cell-phone providers among US customers
Term
Sample Statistic
Definition
Any number based on the sample
Term
Simple Random Sample
Definition
all the objects are put onto one big list, and individual objects are selected completely at random from this list.
Every individual has the same chance of being selected; nobody has a higher or lower priority because of certain characteristics.
Term
sampling frame
Definition
the list of individuals from which the sample is drawn.
Term
Stratified random sampling
Definition
the population is divided into similar groups, and a few people are selected from every group.
Term
Cluster sampling
Definition
the population can be split into groups (clusters) such that each cluster is like a mini- population. Several clusters are chosen at random, and all objects within the chosen clusters are sampled.
Term
systematic sample
Definition
created by selecting every 10th, 50th, 100th, etc. individual.
The selection should start with a randomly selected individual.
Term
Population
Definition
The entire group you would like to study
Term
sampling frame
Definition
the list from whom the sample will be chosen
Term
Sample
Definition
the people who respond and take part in the survey.
Term
Nonresponse bias
Definition
People who don’t respond differ in a systematic way from those who do respond. A good sample was initially chosen, but many of the chosen people can’t be reached or don’t respond.
Term
Voluntary response bias
Definition
The sample is entirely self-selected -- people volunteer themselves to become part of the sample.
Term
Undercoverage
Definition
Certain characteristics of the population is entirely missing from the sample, or has a much smaller proportion than in the population.
Term
Convenience sampling
Definition
occurs when we ask individuals who are convenient without making any effort to randomize. For instance, asking the first 100 people you see rather than choosing a random sample.
Term
Frequency table
Definition
analyzing categorical data. This records the counts for each category.
Term
Relative frequency table
Definition
displays the percentages in each category rather than the counts.
Term
Bar Charts
Definition
shows the counts for each category.
It would not be a problem for a bar chart if people chose more than one answer, or if there were a large number of categories.
Term
Pie Charts
Definition
should be used when the focus is on percentages rather than actual counts, e.g. market share.
Choosing more than one answer would be a problem
Term
contingency table
Definition
displays one variable in the columns and a second variable in the rows.
Term
modes
Definition
Peaks or humps seen in a histogram
one main peak is called unimodal, two peaks – bimodal, three or more – multimodal.
Term
Histogram
Definition
Unlike a bar graph, there are no gaps between the bars
Term
uniform
Definition
all the bars approximately the same height, there is no mode
Term
symmetric
Definition
the halves on either side of the center look (approximately) like mirror images.
Term
skewed
Definition
If one tail stretches out longer than the other,
to the side of the longer tail
Term
mean
Definition
a good measure for unimodal, symmetric distributions. It is commonly referred to as the “average”.
very sensitive to outliers or skewed data.
skewed= gets pulled towards the longer tail
Term
Median
Definition
The value that splits the histogram into 2 equal pieces. "resistant" because it isn't affected by outliers
Term
Quartiles
Definition
the values that enclose the middle 50%. 25% of the data fall below the first quartile, Q1, and 25% are above the third quartile, Q3.
Q1 | Median | Q3
Term
IQR
Definition
Q3-Q1
Term
Standard Deviation
Definition
a measure of the average distance of points from the mean (center)
Term
Median & IQR
Definition
If the shape is skewed, or if there are outliers,
Term
Mean & Standard deviation
Definition
If the shape is unimodal and symmetric and no outliers are present
Term
five-number summary
Definition
consists of the min and max, Q1 and Q3, and the median.
Term
Upper Fence
Definition
Q3 +1.5 IQR
Term
Lower Fence
Definition
Q1 −1.5 IQR
Term
Z score
Definition
tells us how many standard deviations a data point is from its mean
A z-score greater than 3, or less than −3, is very unusual and provides another method of identifying outliers.
Term
probability
Definition
an event is its long-run frequency
it is a number between 0 and 1
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