Statistics Flashcards
What is a null hypothesis?
There is no significant difference between 2 sets of data
What is the null hypothesis of the correlation coefficient?
There is no significant correlation …
When would you use the chi-squared test?
Comparing observed and expected values
What level of probability do scientists always use?
0.05
What does a 0.05 probability show?
95% confidence difference is significant and 5% due to chance
What are degrees of freedom?
The number of variables that are free to change
How do you calculate the dof for chi-squared test?
(n)-1
When do you reject the null hypothesis?
When your calculated value is higher than your critical value at 0.05 probability
What are the statistical analysis steps?
Null hypothesis Select appropriate test Carry out calculation Dof Compare calculated value to critical value
What is the chi-squared equation?
(observed-expected)^2
Sum of ——————————–
Expected value
How do you get the observed value?
From the question
How do you get the expected value?
Use ratio given
What should your table look like for calculating chi-squared?
O E O-E (O-E)^2 (O-E)^2/E
When would you use a t-test?
When looking for a significant difference between 2 sets of data
What is the equation for SD?
√Σ( each score - mean)^2
———————————
number of values - 1
What is the equation for t-test?
(x1 - x2) ----------------------- √(s1)^2 (s2)^2 ---------- + --------- n1 n2
x1 = mean value of 1st sample x2 = mean value of 2nd sample s1 = SD 1st sample s2 = SD 2nd sample n1 = no. of measurements 1st sample n2 = no. of measurements 2nd sample
What is the first SD within and tell you?
68% of data is either +/- from mean
When do you use the correlation coefficient test?
If there is a significant correlation between 2 variables
What must the r value for correlation coefficient always be?
Between -1 and +1
What is the R value if points increasing linear?
+1
What is the R value if points decreasing linear?
-1
What is the R value if points are scattered and random?
0.0
What is equation for correlation coefficient?
LOOK IN BOOK + LEARN
What should the table look like for correlation coefficient?
X Y X^2 Y^2 XY
TOTAL
