HIM 3200 Midterm Review. Dr. Burton. Midterm review. Types of data Normal distribution Variance Standard deviation and z scores 2 X 2 table Hypothesis testing H 0 : H A : ttest Pearson r/Linear regression Chi square. Measurements. Frequency Incidence
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Dr. Burton
Numerator
Rate =  x Constant multiplier
The constant multiplier is usually 100, 1000, 10,000 or 100,000.
Types of rates
Incidence rates (i.e. Per 1000)
Prevalence rates (Proportional i.e. 20%)
Incidence density (frequency of new events per person time)
Denominator
Observer No. 1
Positive
Negative
Total
a
b
a + b
Positive
Observer
No. 2
d
c
c + d
Negative
a + c
b + d
a+b+c+d
Total
+ _ + A B A + B  C D C + D A + C B + D
Sensitivity = A/(A + C)
Specificity = D/(B + D)
False positive rate = B/(B + D)
Falsenegative rate = C/(A + C)
Positive predictive value = A/(A + B)
Negative predictive value = D/ (D + C)
Accuracy = (A + D) / (A + B + C + D)
Strongly agree, agree, neutral, disagree, strongly disagree
a b c d e
1 2 3 4 5
(xi)
Mean = x
Ni
Sum =
Observed values = xi
Total number of observations = Ni
Number of observations or N 26
Initial HDL values 31, 41, 44, 46, 47, 47, 48, 49, 52, 53, 54, 57, 58, 58, 60, 60, 62, 63, 64, 67, 69, 70,
77, 78, 81, 90 mg/dl
Highest values 90 mg/dl
Lowest value 31 mg/dl
Mode 47, 48, 58, 60 mg/dl
Median (57 + 58)/2 = 57.5 mg/dl
Sum of the values (xi) 1496 mg/dl
Means, x 1496/26 = 57.5 mg/dl
Number of observations or N 26
Initial HDL values 31, 41, 44, 46, 47, 47, 48, 48, 49, 52, 53, 54, 57, 58, 58, 60, 60, 62, 63, 64, 67, 69, 70,
77, 78, 81, 90 mg/dl
Highest values 90 mg/dl
Lowest value 31 mg/dl
Mode 47, 48, 58, 60 mg/dl
Median (57 + 58)/2 = 57.5 mg/dl
Sum of the values (xi) 1496 mg/dl
Means, x 1496/26 = 57.5 mg/dl
Interquartile range 64 – 48 = 16 mg/dl
(xi  x)
N
2
(xi  x )
2
s
=
Degrees of Freedom
N 1
2
(xi  x )
N 1
Measures of dispersion based on the Mean.Number of observations or N 26
Initial HDL values 31, 41, 44, 46, 47, 47, 48, 48, 49, 52, 53, 54, 57, 58, 58, 60, 60, 62, 63, 64, 67, 69, 70,
77, 78, 81, 90 mg/dl
Highest values 90 mg/dl
Lowest value 31 mg/dl
Mode 47, 48, 58, 60 mg/dl
Median (57 + 58)/2 = 57.5 mg/dl
Sum of the values (xi) 1496 mg/dl
Means, x 1496/26 = 57.5 mg/dl
Interquartile range 64 – 48 = 16 mg/dl
Sum of squares (TSS) 4,298.46 mg/dl
Variance, “s” squared 171.94 mg/dl
Standard Deviation, s 171.94 mg/dl = 13.1 mg/dl
3
2

+2
+3
+
3
2
1
1
2
3
0
Z scores
H0 True
H0 False
a
b
Correct
Type II
Error
Accept H0
Decision
d
c
Correct
Type I
Error
Reject H0
Alpha error: rejecting the null H0 when it is true
Beta error: accepting the null H0 when it is false
(probability that a test detects differences that actually exist) can be determined by using the formula 1 – beta (1  )
80% is usually acceptable
1. State question in terms of:
H0: no difference or relationship (null)
Ha: is difference or relationship (alternative)
2. Decide on appropriate research design and statistic
3
2

+2
+3
+
Z scores
3
2
1
1
2
3
0
Probability
Upper tail .1587 .02288 .0013
Twotailed .3173 .0455.0027
Student’s t –test: to compare the means of two small (n < 30) independent samples.
Paired ttest: to compare the means of two paired samples (e.g. before and after)
F – test: to compare means of three or more samples or groups.
ChiSquare test: comparing two or more independent proportions.
Correlation coefficient: measures the strength of the association between two variables.
Regression analysis: Provides an equation that estimates the change in a dependent variable (y) per unit change in an independent variable (x).