research lecture 4 Flashcards
what are methods for organizing and summarizing data
descriptive statistics
what is a descriptive value for a population called
parameter
what is a descriptive value for a sample called
statistic
what is the first task for a researcher after collecting the data
organize and simplify the data to get a general overview of the results
one method for simplifying and organizing data is to construct a
frequency distribution
what presents an organized picture of the entire set of scores, and it shows where each individual is located relative to others in the distribution.
frequency distribution
what is used when a set of scores covers a wide range of values.
Grouped frequency distribution
Grouped frequency distribution and frequency destruction are frequently displayed as what
histograms
If the scores in the population are measured on an interval or ratio scale and the N is large, it is customary to present the distribution as a
smooth curve
the smooth curve emphasizes the fact that the distribution is not showing what
the exact frequency for each category
how would you like the shape of your data to be
symmetrical
what shape is when the two sides are close to mirror images of each other…
symmetrical
what shape is when scores pile up on one side of the distribution, leaving a “tail” of a few extreme values on the other side.
skewed
scores bunched at low values with the tail pointing to high values ais called what kind of frequency distribution
positive skew
scores bunched at high values with the tail pointing to low values is called what kind of frequency distribution
negative skew
what kind of kurtosis is frequency distribution is a higher/ thinner peak
leptokurtic
what kind of kurtis is frequency distribution is a lower/ broader peak
platykurtic
which kurtosis frequency distribution is hard to get significance and has increase variability
platykurtic
which kurtosis frequency distribution has better significance and doesn’t have a high variability
leptokurtic
what is a statistical measure that describes the center of the distribution and represents the entire distribution of scores as a single number.
central tendency
what are the 3 commonly used techniques from measuring central tendency
the mode , median and mean
which central tendency is the most frequent score
mode
which central tendency is have 2 modes called anf having several modes
bimodal and multimodal
what is defined as the most frequently occurring category or score in the distribution.
the mode
what is the mode appropriate for
nominal, ordinal, interval, or ratio level data.
if teh score in a distribution are listed in order form smallest to largest , what is defined as the midpoint of the list
the median
what is the median appropriate for
ordinal, interval, or ratio level data.
what is one advantage of the median
that it is relatively unaffected by extreme scores
what is a con for the median
doesn’t tell u the significant difference
what is the most commonly used measure of central tendency.
the mean
Computation of the mean requires scores that are numerical values measured on an…
interval/ratio scale
when a distribution contains a few extreme scores (skewed) the mean will be pulled toward the ___
extremes
when do you not report the mean
with data from a nominal score or ordinal scale
Because the mean, the median, and the mode are all measuring central tendency, the three measures are often ___ related to each other.
systematically
in a symmetrical distribution what will always be equal
mean and median
in a skewed distribution where will each central tendency be (mean , median and mode)
the mode will be located at the peak
mean is usually closer to the tail
median is in between the mean and mode
what serves both as a descriptive measure and as an important component of most inferential statistics
variability
what is it called when variability measures the degree to which the scores are spread out or clustered together in a distribution.
descriptive statistic
what is it called when variability provides a measure of how accurately any individual score or sample represents the entire population.
inferential statistics
what does less variability mean
better representation
what is the difference when the population variability is small and large
When the population variability is small, all of the scores are clustered close together and any individual score or sample will likely provide a good representation of the entire set.
On the other hand, when variability is large and scores are widely spread, it is easy for one or two extreme scores to give a distorted picture of the general population.
what are the 2 ways that variability can be measure with
the range and SD/ variance
variability is determined by measuring the ___
distance
what is the total distance covered by the distribution, from the highest score to the lowest score.
the range
For the data set: 2, 5, 7, 9, 10….the range is
10-2 or 8
what measures the standard (average) distance between a score and the mean.
standard deviation
what kind of significance does a large standard deviation have
none
what kind fo significance does a small standard deviation have
some sig
why does a large SD have a decreased significance
increase variability
decreased number of participants
decreased difference in means
if you want to increased significance what can you do
- decreased variability but decreased SD and variance
- increased the number of participants
- increased the difference of means
what percent of of the scores will be within 1 +/- standard deviation of the mean for a normal distribution
70%
what percent of of the scores will be within 2 +/- standard deviation of the mean for a normal distribution
95%
what percent of of the scores will be within 3 +/- standard deviation of the mean for a normal distribution
99%
what does the z score tell you
exactly where the score is located relative to all the other score
if the z score is positive what does that mean ? negative ?
if it is postivie that mean X value is located about the mean and if it is negative then the X value is located below the mean
The numerical value of the ____ corresponds to the number of standard deviations between X and the mean of the distribution.
z score
a score that is located 2 standard deviations above the mean will have a z score of what
+2.00
what z score always indictes a location above the mean by 2 standard deviations
z score for +2.00
when you change the population score to the population of z scores on the graph does the graph change
no
what is the formula for computing the z score for any value of x
z= X (your score) - the mean / standard deviation
You scored a 82 on a test with a mean score of 70 and a standard deviation of 12. Your z-score will be
1+ bc the standard deviation is 12 and the mean is 70 and you scored a 82 which is 12 above 70 which is the SD so u go up 1 SD from the mean
You scored a 70 on a test with a mean score of 70. Your z-score is
0
The fact that z-scores identify exact locations within a distribution means that z-scores can be used as what 2 statistics
descriptive statistics and as inferential statistics.
what statistics does the , z-scores describe exactly where each individual is located.
descriptive
what statisitcs does the z-scores determine whether a specific sample is representative of its population, or is extreme and unrepresentative
inferential
what is the advantage of standardizing distributions
that 2 or more different distributions can be compared
N=60, Mean=83, Standard Deviation=10, what is the Z-score for 83?
0
N=32, Mean=120, Standard Deviation=23, what is the Z-score for 143?
+1
• N=1000, Mean=100, Standard Deviation=8, what is the Z-score for 92?
-1
N=50, Mean=50, Standard Deviation=10, what value has a Z-Score of -2
30
what are methods for using sample data to make general conclusions (inferences) about populations.
inferential statistics
for inferential statistics what does the research begin with and what does the actual research do
begins with a question about a population and the actual research is conducted using a sample
Rather than just describing the sample data (descriptive statistics)…inferential statistics use the sample to do what
infer something about the population in terms of probability
When a set of scores is represented by a frequency distribution and that distribution is similar to a normal distribution, probabilities can be defined by
proportions of the distributions
Probability =
Proportion
When graphed, probability can be defined as what
the proportional area under the curve.
Drawing a vertical line through a normal distribution divides the distribution into two sections what is the larger section called and what is the smaller sections called
larger section is called the body and the smaller section is called the tail
what will give you ALL POSSIBLE proportions/probability for every z score.
the unit normal table
so if you know the z score what can u look up ?
proportion/ probability
if you know the proportion/probability what can you look up
z score
if the z score is 1.96 how much of the area is in the tail
2.5%
If we think if the area in the tails when we use 1.96 (to the right)…and -1.96 (to the left)…there would be a total of ___ % in the 2 tails.
5
Do we use the normal distribution when running statistical tests
no
what theory is as the sample size increases it approaches a normal distribution.
central limit theorem
the smaller the sample size the smaller the ___ will be on the graph
tail
Population data can be ANY size and shape….but thanks to the central limit theorem…
single sample of 30+ it will be very close to a normal distribution
N>30 is only ___ assumption for parametric testing
1
A sample size of ___ is often used as a rule of thumb for statistics since the sample of scores will be approximately normal.
30
what software do we use for a better estimate of the number or participants needed for a study
g power
If we are comparing more than two groups or time periods, or we have a factorial research design (2+IV) we run a statistical test called and what distribution does it use
ANOVA and it uses the F distribution
if we are comparing 2 groups or two time period we run which test ad what distribution does it use
t test and uses t distribution
if we are comparing the portions of people in different groups we use which distribution
the chi square
what test compares observed frequencies to what would be considered the expected frequencies
chi square
what is a value that describes the difference between the sample mean and the true population
standard error of the mean
what measure the amount of variability or dispersion for a set of data from the mean ?
SD
what measures how far the sample mean of the data is kiley’s to be from the true population mean
standard error of the mean
is the standee error of the mean smaller or larger then the SD
always smaller
a small standard error of the meal is interpreted as what
less sampling error
as the sample size increased what happens to the standard error of mean if the SD stays the same
it decreased
what is the equation for standard error of the mean
SD / square root of N (sample size)
most researchers will report what estimation
point estimation and interval
what estimation is a mean of your sample
point
what estimation is a span of number values that incorpates the mean
interval mean
what estimation is the sample mean…and it is used to estimate the population me
point
My sample of entering DPT students has an undergraduate GPA of 3.4 (95%CI: 3.2-3.6), so I will assume that the population of all DPT students has a GPA of 3.4.. what foes the CI mean
I am 95% confident that the real population mean is between 3.2 and 3.6.
what is a range of numbers inferred from the sample that has a known probability of capturing the true population parameter over the long run (ex/ over repeated sampling).
interval estimate AKA a confidence interval
The “beauty” of adding confidence intervals to your results is that the reader knows the probability that what
the true mean has been reported
Functional Outcomes in those with CVA and TBI after residential inpatient care at NeuroRestorative in Houston
Is this a prospective study?
Is this a 1b level study?
Is this a truly experimental study?
Could this study be reviewed using a PEDro scale?
yes and the. no 3x
If the calculated t-score is greater than our calculated t-value…it’s ____ . (2-tail)
significant
which sample mean is more likely to closer to the population mean?
which ever sample mean is closer to the actual mean
in box plots what does the box show
the median
the upper and lower quartile (25% and 75%)
the limits within which t middle 50% of scores lie
in box plots what does the box show
the median
the upper and lower quartile (25% and 75%)
the limits within which t middle 50% of scores lie
in a box plot what does the whiskers show u
the range of scores
th eli it’s within which the top and bottom 25% of the scores lie
in the error bar charts the bar usually showwhat score
the mean
in the error bar charts the bar usually showwhat score
the mean
The error bar displays the precision of the mean in one of three ways:
› The confidence interval (usually 95%)
› The standard deviation
› The standard error of the mean (SEM)
no
