linear correlation
Message posted by sanja on June 16, 2000 at 12:00 AM (ET)

I need several examples of variables in which there is a significant linear correlation either positive,negative, or both. Discuss the relationship between the variables and what makes them correlate to such a degree ?

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Re: linear correlation
Message posted by Stuart Jones on June 23, 2000 at 12:00 AM (ET)

1st things 1st. You can only have either a positive correlation, a negative correlation, or no correlation at all.

An obvious linear correlation is that of height and weight. It stands to reason that the taller you are, then, on average, the more you will weigh. Therefore the correlation is positive. If you do a scatter graph of your friend's weights against heights, this should be confirmed. Basically what a positive correlation says is "As one set of data eg height increases, then the other set of data increases too"

An example of negative correlation is this. Suppose we had a pest control problem. It stands to reason that the more poison we put down, the more pests we kill. So if we plotted on a graph Amount of Poison (y-axis) aganst Pest population, we would expect to see that the more poison we use the smaller the pest population will become.
Basically what a negative correlation says is "As one set of data eg Amount of poison increases, then the other set of data decreases too"

In statistics we use what is termed a "correlation coefficient" to measure the relationship between the data. This number is always between the numbers of -1 and 1. 1 is a perfect positive correlation and -1 is a perfect negative correlation. If you get a correlation coefficient of 0 this means that there is no relationship between the 2 sets of data. Statisticians often use hypothesis testing to test whether there are relationships between the 2 different types of data.

Re: linear correlation
Message posted by k banna on June 26, 2000 at 12:00 AM (ET)