Stat 503 Exam Questions with Correct Answers
Numeric or quantitative variables - Answer-- describe traits that are measured or counted
- have magnitude and units
- are either continuous or discrete
- Numeric variables can be treated as categories if:
-- The variable is discrete and the number ...
Stat 503 Exam Questions with Correct
Answers
Numeric or quantitative variables - Answer-- describe traits that are measured or
counted
- have magnitude and units
- are either continuous or discrete
- Numeric variables can be treated as categories if:
-- The variable is discrete and the number of possible values is small. (e.g. number of
children in a household)
-- Only a few specific values are included in the data by design (e.g., three dosage
levels in an experimental drug trial).
Continuous numerical data - Answer-- take on any real-number value within some
range.
- Between any two values of a continuous variable, an infinite number of other values
are possible.
- ratio and rates are always continuous even if they are ratios of counts
Discrete variables - Answer-- counts
- Their units can not be subdivided
Categorical or qualitative variables - Answer-- describe categories or classifications
- can be nominal or ordinal
- can be represented with numbers, but they are still not numeric.
- If you work with categorical data, it's a good idea to record meaningful category labels
instead of numeric codes.
- can be represented with numbers, but they are still not numeric
- Numerical data can be reduced to categorical data by grouping, though the result
contains less information.
Nominal variables - Answer-- have no inherent ranking (color, species, diet type)
- describe categories that don't have obvious, inherent rankings associated with them
Levels of ordinal variables - Answer-ranked and can be ordered. (age class, dosage
level, Likert scales)
The treatment variable - Answer-the one manipulated by the researcher is the
explanatory variable
, An explanatory variable - Answer-what you manipulate or observe changes in (e.g.,
caffeine dose), while a response variable is what changes as a result (e.g., reaction
time)
One major use of statistics is to... - Answer-relate one variable to another by examining
associations between variables and differences between groups.
A study is experimental if... - Answer-the researcher assigns different treatment groups
in an experimental study
observational - Answer-- If values of the explanatory variable are not randomly
assigned, the data...
- can show association but cannot show cause-and-effect relationships.
experimental data - Answer-need to show causation is logical, not statistical
the frequency distribution - Answer-describes the number of times each value of a
variable occurs in a sample
why do we need statistics? - Answer-- biologists study the properties of living things
- measuring these properties is a challenge
variation - Answer-an inherent component of all living systems
system - Answer-anything composed of multiple interacting parts
constraints of stats - Answer-time and funding
uncertainty - Answer-variation + incomplete information
- sampling can bring it to the project
- probability or likelihood
Statistics - Answer-- the study of methods to describe and measure aspects of nature
from samples
- a branch of science chiefly concerned with the collection, analysis, interpretation, and
presentation of empirical data
- provides tools to turn raw data into knowledge and understanding
- helps us recognize and describe the patterns in our data and helps us decide how
certain we are that our data reflect reality
- it is about estimation
estimation - Answer-the process of inferring an unknown quantity of a population using
sample data
- a.k.a. statistic
- a related quantity calculated from a sample
- approximation of the truth
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