Biostatistics Study Guide

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Kalista Cox
Biostatistics Study Guide
Quiz #1
- Research
• collecting of information about a particular subject
- MATLAB
- Chapter 2: How to Summarize Data
• Populations
- all individuals of interest characterized by parameters
• Sample
- actually observed
- drawn from random from the population
• Levels of Measurement (variable scales)
- interval (continuous)
• ratio has a true 0
• ex: temperature (degrees), mmHg, days, N, m
- ordinal (ranked)
• numbers assigned to objects repress rank order
• ex: tumor grading scale
- nominal (categorical)
• no arithmetic relationship between the different classifications
• ex: M/F, dead/alive
• Normal/Gaussian Distribution
- interval data
- probability model
- formula:
Kalista Cox
- Attributes of normal distribution
• symmetric about the mean
• mean=median=mode
• mean and variance/standard deviation characterize the distribution
• 68% of data falls between μ- and μ+
• 95% of data falls between μ-2 and μ+2
• 99% of data falls between μ-3 and μ+3
• area under normal curve between two points reflects probability
- area under entire curve = 1.0 or 100%
- Analyzing Interval Data
• variance
- mean = x_
• standard deviation of a population
• standard deviation of a sample
Kalista Cox
• standard error of the mean
- estimates whether the mean computed from a random sample estimates
the true mean of the population
-
Population : SEM
= σX
Sample :
=
SEM
sX
=
=
σ
n
s
n
• median= 50th percentile
• pth percentile= (n+1)/(100/p) observation
• percentiles
2.5th percentile
mean - 2 standard deviations
16th percentile
mean - 1 standard deviation
25th percentile
mean - 0.67 standard deviations
50th percentile (median)
mean
75th percentile
mean + 0.67 standard deviations
84th percentile
mean + 1 standard deviation
97.5th percentile
mean + 2 standard deviations
• z- scores
- z = (x-u)/sigma
- usually equivalent to number of standard deviations from the mean
• Plotting: histograms and box plots
- Box Plots
• IQR= Q3-Q1
• Q1= 25th percentile
Kalista Cox
- minimum data value within 1.5*IQR below 25th percentile
• Q3 = 75th percentile
- maximum data value within 1.5*IQR about 75th percentile
• Checking for normal distribution
- Check how well percentiles match
• compare 25th to 75th and etc
Name: _______________​
Kalistacox ​________
BME 22000 Biostatistics and Research Methods
Homework #1 due 9/5/18
Use the MathWorks website (tutorials, videos, etc.) and consult Matlab Help to answer the
following questions. Review course syllabus for class policy on collaborating – do your own work!
1. What is the Command Window?
The
window
command
values
and
variables
of
where
is
MATLAB
type
you
such
commands
calculations
as
,
equations
,
.
2. Name 4 types of data file formats that can be imported into Matlab.
4
of
types
Matlab
Matlab
files
Text
are
files
that
formats
file
data
.
files
spreadsheet
,
Images
,
into
imported
be
can
and
,
3. What is the default data type for numeric data in Matlab?
Matlab
point
floating
data
numeric
stores
-
double
a
as
precision
-
.
4. Briefly describe one way to view variable data in Matlab.
One
at
view
to
way
variable
browser
workspace
the
in
data
Matlab
which
,
show
will
look
to
is
to
of
screen
your
values
their
and
variables
the
right
the
5. What is a .mat file?
A
mat
.
such
is
file
contains
saved
a
as
that
one
Matlab
variables
a
workspace
formatted
data
,
.
6. Name 4 types of plots that can be created in Matlab.
4
of
types
line
include
that
plots
plots
plots
polar
,
mesh
,
in
created
be
can
plots
command
Matlab
command
With
.
previous
running
shows
window
history
history
commands
copying
,
do
car
you
.
of
history
a
commands
,
such
and
deleting
8. What does the command clear all do?
command
The
the
as
"
command
dear
all
"
clears
and
window
windows
open
workspace
9. How do you define a variable in Matlab?
You
You
define
type
a
"
variable
variable
=
"
by setting
followed
by
that
equal
variable
whatever
the
to
variable
specific
a
is
defined
such
,
.
value
as
or
.
plots
commands
things
many
previous
contour
and
,
7. What can you use the Command History window for?
The
Matlab
function
.
run
.
in
as
history
.
,
10. Name 2 limitations of variable names.
Cannot
D
same
with
start
cannot
2)
the
be
number
a
Matta
a
as
name
;
with
start
must
keyword
b
function
or
letter
a
11. Give a specific example of a command that creates a column vector of your choice (i.e, you define the vector).
You
example
For
3
by
I
,
numbers
by
using
t.
C
=
x
8
.
2
's
brackets
square
semicolon
a
command
the
vector
column
by
vector
column
a
separating
and
this
create
can
;
-
output
would
]
4
8
X=
I
,
12. Do you need a specific toolbox to perform a one-way analysis of variance? If so, what toolbox do you need?
to
toolbox
Learning
of
and
statistics
the
need
specifically
You
perform
Machine
analysis
one-way
a
variance
13. Name 2 aspects of the MathWorks website that you found useful that you would recommend to other students.
Firstly
search
the
search
can
and
you
would
I
within
you
course
,
functions
because
.
would
the
,
to
retain
what
practice
you
documentation
of
section
support
Matlab
specific
I
the
recommend
also
notes
recommend
problems
are
Matlab
learning
within
,
where
certain
on
the
ramp
on
it
better
.
.
topics
2
-
hour
help
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