Psych Statistics Flashcards

Terms Definitions
xbar+1, +2, +3 numbers
50%tile34.13%13.59%2.15%.14%
p>.05
retain (fail to reject) null
P value represents...
tail area probability
ANOVA
stat. use for multiple IV's
z-score formula
z= (x-xbar)/ standard dev.
Non-Normal(Bimodal Curve)
m-shaped. has two modes.
z = x-Mu/sigma (for populat)--->z=x-xbar/ strd dev (for sample). This is known as a ____ ______
transformation scaling
If cards are drawn without replacement, the probability that player 1 gets a 1 is....
1/3
type 1 error
increases as alpha increases=rejecting the ho when it is true=stating IV caused the result when it was really due to chance
range
the simplist measure. the difference between the highest and lowest scores in the distribution
cumf
the cumulative frequency. the number of scores at or below any given score
How do you solve for z?
(null-alternative)/Strd Error
Continuous random variables will have what kind of distribution?
Normal distribution
For multiple choice probs where 4 choices are present, what is the probability that a student makes all 5 problems by sheer guessing?
n=5p=1/4(p)^(n)(1/4)^(5)
Which distribution is used to determine the p value?
sampling distribution
Deviation
the difference between a given score and the mean of the distribution D=x - xbar
Non-Normal(Ogive Curve)
s-shaped curve. either all high scores or all low scores.
f
the frequency with which each score occurs in the data
Normal(Leptokurtic Curve)
small standard dev. (scores all bunched up around mean)
percentiles can also be seen as...((13.59%))
probabilities ((P=.1359))
type 2 error
increases as alpha gets smaller=failing to reject t he Ho when it is really false=stating the result was due to chance when was due to IV
mean
mathematical average of a group of scores, the sum of the scores divided by the number of scores(most vulnerable to extreme scores)
____ error is controlled and minimized by setting the __ level in hypoth testing.
Type 1, alpha
how large does sample size need to get for the central limit theorem to apply?
30
CLT maintains that...
all sampling distributions of any size or kind will be approximately normal regardless of the original
cumprop
the proportion of scores at or below any given score ( take the cumf and divide by the total number of scores)
standard deviation
the avergae deviation of all scores from the mean
Variance
the square of a scores deviation from the mean d2=variance.
%ile
percentage of scores at or below any given score
alpha level
the probability of an event occuring by chance at which one is willing to reject the Ho
What type error if:the null is true but you reject it?
type I
Something that is statistically significant...
-is not necessarily scientifically significant. Stats just lets us make a best educated guess.-occurs whenever p is less than alpha and you reject the null.
What type error if:the null is false but you retain it?
type II
Ho is a ....
statistical decision. It's the true state of nature and has not been proven.
How do you calc the binomial p=8 when n=8 and p=1/2
(1/2)^8
calculating standard dev.
1. find mean of distributon2. create freq. dist. chart -x(score) -f(freq.) -d(deviation, the score-mean) -d2(variance, deviation squared) -fd2(variance * freq)1 add up all the numbers in fd22 divide dum of fd2 by N3 take square root of result
Expressing p-value
p value = p (observed data or more extreme given the null) Alternativelypval = p(observed or more extreme | Ho)
type II error
retain the null when the null is false=Beta
Hypothesis testing is also known as ....
null hypothesis significance test
Type I error
reject the null when the null is trueType I is what we try to minimize=alpha
Does a sampling distribution have anything to do with actual data?
not reallly. The sampling distribution is a hypothetical distribution
If the original x was normally distributed, what kind of distribution will be obtained?
Standard (Unit) normal distribution
Frequentist methods
are the standard. Ho and H1 are not on equal footing, bias is in favor of null. Decision is based upon p value.
Logic of inferential statistics
to decide if the difference between the experimental group mean and the control group mean was caused by the IV or just chance
definition of standard error
standard error = strd dev of the sampling distribution
steps in taking a binomial distribution to a standard normal distribution (with z scores)
1. W/ binomial distribution, get tail-area variables2.W/ tail area probability (p) scale to a standardized z score3. Z scores are used in a unimodal, normal distribution
above = below =
will have a z that is positivewill have a z that is negative
The p value is the ...
probability of obtaining a sample mean equal to the observed sample mean or one that is more extreme UNDER THE NULL HYPOTHESIS
For these mutually exclusive events, which rule is used?1. Player 1 gets 1 and P2 gets 1.2. Player 1 gets 2 and P2 gets 13. Player 1 gets 3 and P2 gets 1
For exlusive events, the addition rule is used.in this case:P(1,1 or 2,1 or 3,1) = P(1,1) + P(2,1) + P(3,1)
Standard error represented as:
SE = strd dev/ sq rt of n
mean is 10. sd is 2. what is score at z=+2
14
Can hypothesis testing tell which of the hypotheses being tested is true?
No. Hypothesis testing can only provide an educated guess about which one is likely to be true.
For which kind of variable is the binomial distribution used?
discrete random variablesex. correct or not correct
smaller portion column in the normal distribution table refers to...
area from z to pos infinity
What is type II error?
Type II (Beta) is the prob of retaining Ho when it's false.
when p< alpha, what do we with the null?
p< alpha, reject null
Ho is correctFail to reject the Ho
assert difference is due to chance
If cards a drawn with replacement...
Each card has an equal chance of being drawn.
___ refers to the normal distribution probability.____ of ____ is not a probability.
An Area refers to the normal distribution probability.height of curve is not a probability.
How do you interconvert between the sm. portion and the p value?
.081 is sm. portion8.1% is p value
Probability is determined as an ___ not a ___
Probability is determined as an area, not a height
8 grades are given for two different students. The instructor would like to know if the understand the material equally well. What are the null and alt hypoth?
Ho= both understand mat'l equally wellH1= 1 of the students understood the mat'l better than the other
What kind of distribution would be used for height & weight measurements?
Normal, because height and weight are continuous random variables.
A z = -1.2 means...
the original x is below the mean by 1.2 standard deviations.
What do a series of normal curves with different means but the same strd deviation look like?
different means = each line that vertically bisects each curve at its peak is at a different location.The same strd dev = same width
How is z useful in determining location?
Z gives you a relative location in terms of how far your your number is above or below the mean
What terms can you use when referring to Ho?
reject, retain, or fail to reject CANNOT EVER say accept. The use of accept is confined to the alternative hypothesis.
How calc the P(x and y)?
P (x and y) = P(x |y) * p(y)
How do you know which value to use in the alternative hypoth?
Whichever number corresponds to results following the treatment or intervention.
Between what two scores do the middle 95% of sample means fall on a scale in which the mean is 100, std dev is 15, and sample size is 25? In this question, how do you determine the middle 95%?
100-95 = 5 percent, so there's five percent to be divided up between the two ends of the distribution.5/2 = 2.5Convert 2.5 to a propotion2.5/100 = .025If this will serve as the left end, make it negative (-.025) and look up corresponding z in the sm portion.At the right end:95 + .025 = .975look in lg portion to find .975, then match this with a z value.
if p>alpha, what happens to the null hypoth?
we will retain (fail to reject) Ho (null).
If you're not asked for a p value, you can do hypothesis testing with z alone. How?
1. Your alpha level will determine the magnitude of your z critical, for alpha of .05, z=1.64, for alpha of .01 z is 2.33.2. The sign of your z crit is determined by a comparison of H1 with Ho. If H1 > Ho, then z crit is pos.3.If the calculated z is GREATER than z critical, then we reject the null. (This is diff than with p in which if calc p is LESS than .05 by the stat decion rule we reject the null).
8 grades of 2 students are given. Nicole gets higher grades six of the times.The instructor would like to know if they understand the material equally well. When calculating probabilites, what 3 P=# should be established?
3 valuesP (when n=8 and p=1/2) =6P (when n=8 and p=1/2) =7P (when n=8 and p=1/2) =8wherep=1/2 was given in probn=total number of grades~I think that you start with P=6 in your calc of binomial probability values be/c its the highest number of superior grades obtained by either of the students. Once you've calc P=6,7,8 in the binomial way, add these 3 probs together and compare the result to .05 to determine retain or reject the null.
The p value is the tail area probability under which hypothesis?
Tail area prob is the null.The large area that remains after you subtract away the tiny sliver of the p is the probability of the alternative probability, but this is NOT considered a p value.
If you don't have independent events, what is the rule that you MUST use?
P(A and B) = P(A|B)*P(B)or P(A and B) = P(B|A) *P(A)
If A and B are independent events, what can we say about P(A |B)?
If A and B are indep, then:P(A|B) = P(A)
for H1P(x bar > x bar observed)Will this calc produce a p value?
No- this is not a tail area, so it's not a p value
P = 0.2What does this mean in terms of a coin toss?
P= 0.2 means that each time there's a 20% chance of heads
For a set of 10 probs, find the sm. # of items that a student has to do correctly to demonstrate that he is not doing them by sheer guessing? For this prob, what are the null and alt hypoth?
Ho=student is doing the probs by guessingH1 = student is not doing the prob by guessing
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