hypothesis
The time period may not affect the correlation coefficient at all. If looking at the correlation between the mass and volume of steel objects, time is totally irrelevant. The effect of the number of variables depends on whether or not the extra variables are related to ANY of the variables in the equation.
makeing the correlation spurious
Statistically, you would need to conduct an experiment in which every single other variable was controlled. Not a feasible option so you control the obvious covariates and examine the residual covariance between the two variables of interest. Even so, you may not find something. For example, the covariance between x and y where y= x2 over any symmetric interval is 0.
controlled experiment
Moderation occurs when the relationship between two variable depends on a third variable. The third variable is referred to as the moderate variable or simply the moderator
A cause and effect relationship between the two variables.
The time period may not affect the correlation coefficient at all. If looking at the correlation between the mass and volume of steel objects, time is totally irrelevant. The effect of the number of variables depends on whether or not the extra variables are related to ANY of the variables in the equation.
'Known' Variables
(1) The masses involved, (2) the distance between the masses.
A controlled experiment can be used to show a cause and effect relationship. ex: an experiment studying the effect of a certain medicine on patients.
If none of the variables are constant (or controls) you have no idea which variable or combination of variables caused the effect.
An experiment is when the researcher manipulates the independent variable and records its effect on the dependent variable whilst maintaining strict control over any extraneous variables. A correlation is a statistical relationship between two or more variables. The researcher makes a change in one of the variables to see what is affected.
makeing the correlation spurious
To show the highest degree of validity of a hypothesis.
The gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
Controlled variables are things that may effect the outcome of an experiment, like temperature are pressure or the amount of some substance used. Dependent variables are those which change due to the conditions mentioned above. These might be speed of the reaction, or the quantity of some product.
No, it would not. It is possible that the statistical model is under-specified and that the variables being studied are all "caused" by another variable.