Introduction of Human Body & Structure of cell.pptx
T test
1. RAK college of Nursing
RAK Medical and Health Sciences University
Seminar on: T-test, independent and paired samples
Course: Statistics for health professionals
Prepared by:
Abdelrahman Alkilani- 15906012
Sultan Sultan- 15906013
Submitted to Dr. Maragatham Kannan, Associate professor
Date of submission: 15/11/2015
2. Objectives
By the end of this seminar, you’ll be able to:
Define T-test
Discuss the merits and demerits of t-test
Identify the independent t-test and discuss
when to use it.
Identify the paired t-test and discuss when to
use it.
Use the correct formulas of t-test
Use the t-test through SPSS
3. T-test
The t-test assesses whether the means of
two groups are statistically different from
each other
4. Merits and demerits
Merits:
– It reduces the possibility of guising the correct
answer .
– It covers greater amount of contents than
matching types test.
Demerits
– it is only appropriate for questions that can be
answered by short responses
– There is a difficult in scoring when the questions
are not prepared properly and clearly
5. Independent t-test
It is a parametric test used to determine if a
difference exists in the means of two groups
on a particular characteristic.
6. Independent t-test
Used when:
– The grouping variables is dichotomous
– The variable measuring the characteristics of
interest is normally distributed.
– The variable measuring the characteristic of
interest in interval or ratio
– The measure of each value of the variable, which
measures the characteristic of interest, constitute
and independent random sample
7. Computing the independent t-test
Need two t-values:
– Calculated t-value
– Critical t-value
If calculated t-value is greater than critical t-
value, then reject the null hypothesis.
8. Computing the independent t-test
Example:
In a study, we want to know whether smokers and
non-smokers have equal brain sizes.
10. Computing the independent t-test
1. State the null and alternative hypothesis.
H0 : There will be no difference in the means of the two
groups.
“smokers and non-smokers have equal brain size”
HA : smokers and non-smokers have unequal brain size
23. Paired t-test
The measurements of the same variable at
two different points are compared.
It can be measured at the same time on two
different people who are matched on some
condition (e.g. age, gender, twins).
24. Paired t-test
Used when:
– There are two measurements of characteristic of
interest.
– The two measures that are compared are
normally distributed or at least 30 pairs.
– The measurement scale is either interval or ratio.
25. Computing the paired t-test
Need two t-values:
– Calculated t-value
– Critical t-value
If calculated t-value is greater than critical t-
value, then reject the null hypothesis.
26. Computing the paired t-test
Pre post Difference
(D)
Difference 2
1 7 6 36
2 6 4 16
1 8 7 49
Sum=17 Sum = 101
29. Computing the paired t-test
Degree of freedom = n-1
= 2
Alpha = 0.05
Critical t from the t- table = 2.92
30. Computing the paired t-test
Calculated t > critical t
6.425 > 2.92
We will reject the null hypothesis. So, there is
a difference between pre and post
34. Paired test using SPSS
As the sig. < alpha
0.023 <0.05
Null hypothesis will be accepted
35. Summary
The t-test assesses whether the means of
two groups are statistically different from
each other
Independent t- test is to determine if a
difference exists in the means of two groups
on a particular characteristic.
Paired samples t-test is a measurements of
the same variable at two different points are
compared
36. Summary
To calculate t-test, we need two t-values:
– Calculated t-value
– Critical t-value
If calculated t-value is greater than critical t-
value, then reject the null hypothesis.
In SPSS:
– analyze for normal distribution
– Perform the test
– If the sig < alpha value, null hypothesis will be
accepted