![Independent and dependent variables are defined within the
research context, a dependent variable in one research
setting may be an independent variable within another.
Example using Social cognitive Theory as our theoretical orientation and variables from the
BRFSS dataset.
Study question # 1 - Does ‘access to health care’ and feelings about ‘having
children’ predict ‘intake of folic acid’?
BEHAVIOR
(# 1 [OM] folic acid - DV)
ENVIRONMENT INDIVIDUAL
(# 3.1 health care coverage - IV) (#18.4 having children- IV)](https://image.slidesharecdn.com/independentanddependentvariables-161206221835/85/Independent-and-dependent-variables-4-320.jpg)
![Study question # 2 - Does ‘access to health care’ and ‘intake
of folic acid’ predict ‘tobacco use’?
BEHAVIOR
(# 7.2 tobacco use - DV)
ENVIRONMENT INDIVIDUAL
(# 3.1 health care coverage - IV) (# 1 [OM] folic acid - IV)
In study question # 1 ‘intake of folic acid’ was our dependent variable
(DV) while in study question # 2 we used ‘intake of folic acid’ as one
of our independent variables (IVs).](https://image.slidesharecdn.com/independentanddependentvariables-161206221835/85/Independent-and-dependent-variables-5-320.jpg)
Independent and dependent variables
- 4. Independent and dependent variables are defined within the research context, a dependent variable in one research setting may be an independent variable within another. Example using Social cognitive Theory as our theoretical orientation and variables from the BRFSS dataset. Study question # 1 - Does ‘access to health care’ and feelings about ‘having children’ predict ‘intake of folic acid’? BEHAVIOR (# 1 [OM] folic acid - DV) ENVIRONMENT INDIVIDUAL (# 3.1 health care coverage - IV) (#18.4 having children- IV)
- 5. Study question # 2 - Does ‘access to health care’ and ‘intake of folic acid’ predict ‘tobacco use’? BEHAVIOR (# 7.2 tobacco use - DV) ENVIRONMENT INDIVIDUAL (# 3.1 health care coverage - IV) (# 1 [OM] folic acid - IV) In study question # 1 ‘intake of folic acid’ was our dependent variable (DV) while in study question # 2 we used ‘intake of folic acid’ as one of our independent variables (IVs).
- 6. Levels of Measurement Variables differ in “how well” they can be measured, in how much measurable information their measurement scale can provide.
- 10. Ratio Ratio variables are similar to interval variables; in addition to all the properties of interval variables, they feature an identifiable absolute zero point. Now I can say on a Kelvin temperature scale that 200 degrees is higher than 100 degrees and that it is twice as high. *A lot of analysis procedures do no distinguish between ratio and interval properties of a measurement scale.
- 11. Categorical vs. Continuous Data Data can be continuous or categorical (discrete)
- 12. Continuous Data A set of data is said to be continuous if the values / observations belonging to it may take on any value within a finite or infinite interval. You can count, order and measure continuous data. For example, height; weight; temperature; the time required to run a mile.
- 13. • Continuous variables are measured on an: – ordinal scale/rank-level – example - on a five-point rating scale measuring attitudes toward abortion, the difference between a rating of 2 and a rating of 3 may not represent the same difference as the difference between a rating of 4 and a rating of 5 – Interval – example - if depression were measured on an interval scale, then a difference between a score of 10 and a score of 11 would represent the same difference in anxiety as would a difference between a score of 50 and a score of 51 – ratio scale – example- Kelvin scale of temperature. This scale has an absolute zero. Thus, a temperature of 300 Kelvin is twice as high as a temperature of 150 Kelvin. Continuous dependent variables are described with measures of central tendency (means, medians, modes), and dispersion (variance, standard deviation, range).
- 14. Categorical Data Represents a set of discrete events, such as groups, decisions, or anything else that can be classified into categories; A categorical variable may also consist of more than two categories. For example, a person's major at RSPH can be categorized as BSHE, EPI, IH, etc. A categorical variable can be ordered or unordered. For instance, a person's level of schooling is an ordered variable; a person's sex is an unordered variable.
- 15. Qualitative Data • Categorical Data are measured on a: – Nominal Scale - (i.e. gender, race, religion, state of residence, make of car) • Dichotomous - dichotomous (i.e. on/off, alive/dead, yes/no, male/female) – Ordinal/rank-order – (i.e. order of participation, arrival for 4 people, class standing) Categorical and dichotomous dependent variables are described with frequencies and percentages.
- 16. Continuous or Categorical • 1) The number of people infected with HIV. Categorical - The number of people infected must be a whole number. • 2) The temperature at which Salmonella is killed. Continuous - The temperature can take on infinitely many values (any decimal is possible). • 3) The number of suicides committed by teenagers. Categorical - The number of suicides must be a whole number. • 4) The number of teenage pregnancies. Categorical - The number of suicides must be a whole number. • 5) The time it takes for a smoker to develop emphysema Continuous. The amount of time can take on infinitely many values (any decimal is possible). 6) The production of fruits and vegetables by weight. Continuous. The weight of the fruits and vegetables can take on infinitely many values (any decimal is possible).
- 17. Categorize the following variables as being qualitative or quantitative, categorical or continuous, and specify the level of measurement: Response time: Quantitative Continuous Interval Rating of job satisfaction: Quantitative Continuous Ordinal Favorite color: Qualitative Discrete Nominal Occupation aspired to: (Qualitative as it stands but could be considered quantitative if rated in terms of expected income, prestige etc.) Discrete Nominal Number of words remembered: Quantitative Continuous Interval