A research hypothesis is a formal statement that predicts the relationship between two or more variable. Research hypothesis are not stated for descriptive research questions. A research hypothesis is stated in comparative and relationship based research question when some evidence exists to show the relationship between two or more variables.
A hypothesis needs to have the following elements.
The population
The suspected cause (Independent variable)
The expected outcome (Dependent variable
The dose-response relationship (if postulated)
Time-response relationship (if postulated)
The hypothesis statement needs to mention about the population in whom the suspected cause that is the independent variable and the outcome that is the dependent variable is being studied. Sometimes the hypothesis also states the dose response relationship or time response relationship between the two variables.
A Variable is any condition that can change or vary in quantity or quality.
Independent variable: stand alone factor / characteristic, not affected by other factors in the study.
Dependent variable: influenced by other characteristics /factors in the study.
Independent or dependent variable are not fixed and vary from study to study.
Example of Research Hypothesis(RH)
RQ: Are there any differences in the biological and psychosocial factors amongst urban slum women of Mumbai aged 40-70 years undergoing breast cancer screening and not undergoing going breast cancer screening.
Type of RQ: Comparative RQ
RH: The biological and psychosocial factors amongst urban slum women aged 40-70 years undergoing breast cancer screening are different from those not undergoing breast cancer screening.
Population: Women aged 40-70 years and above in Mumbai
Independent variable: Biological and psychosocial factors
Dependent variable: Breast cancer screening
Dose/Time response relationship: Not mentioned
State the elements of hypothesis for the Research Hypothesis, “Women who consumed OCPs for less than ten years are at a lesser risk of breast cancer than those who consume OCPs for ten years or more”
Population: Women who consume OC pills
Independent variable: Consumption of oral contraceptive pills
Dependent variable: Occurrence of breast Cancer
Dose/Time response relationship: Duration of consumption of OCPs(<10 years or >=10 years)
Two types of Hypothesis
Null and Alternate Hypothesis.
Alternate hypothesis can be stated either as Directional (One-tailed) or Non-directional (two tailed) Hypothesis.
Null Hypothesis (H0) states that there is NO SIGNIFICANT DIFFERENCE between the two groups.
Alternate Hypothesis (H1) states that there is SIGNIFICANT DIFFERENCE between the two groups. In the alternate hypothesis the difference between two groups can be stated as directional or non-directional hypothesis.
Directional hypothesis states whether the difference is MORE or LESS than the comparison group. Also called as ONE TAILED HYPOTHESIS.
Non-directional hypothesis states that there is SOME difference between the two groups. Also called as TWO TAILED HYPOTHESIS.
Example: Null & Alternate Hypothesis
RQ: “Is there a difference in proportion of women undergoing breast cancer screening amongst the middle and high socio-economic groups?”.
H0: “There is no significant difference in proportion of women who undergo breast cancer screening amongst the middle and high socio-economic group”
H1: “The proportion of women who undergo screening amongst the middle income group is significantly lower than the high socio-economic group” (One Tailed Hypothesis)
H1: “There is some significant difference in proportion of women who undergo screening amongst the middle and high socio-economic group” (Two Tailed Hypothesis)
State the Null & Alternate Hypothesis for the RQ:
“Is there any difference in proportion of youth smokers who studied upto 7th standard and those who completed 10th standard?”
N0: “There is no significant difference in proportion of youth smokers who studied upto 7th standard and those who completed 10th standard”
N1: “The proportion of smokers is significantly higher amongst youths who studied upto 7th standard as compared to those who completed 10th standard” (One Tailed Hypothesis)
N1: “There is some significant difference in the proportion of smokers amongst youths who studied upto 7th standard as compared to those who completed 10th standard” (Two Tailed Hypothesis)
There is no significant difference between examinations score of students availing library facilities and not availing library facilities.
Answer
Null Hypothesis
“Women who consumed OCPs for less than ten years are at a lesser risk of breast cancer than those who consume OCPs for ten years or more”
Answer
One tailed Alternate Hypothesis
There is some difference in the dietary habits of school children of rural and urban areas.
Answer
Two tailed Alternate Hypothesis