Conclusion: There is sufficient evidence to conclude that there is a significant linear relationship between the third exam score ( x) and the final exam score ( y) because the correlation coefficient is significantly different from zero.īecause r is significant and the scatter plot shows a linear trend, the regression line can be used to predict final exam scores.Decision: Reject the Null Hypothesis H 0.The p-value, 0.026, is less than the significance level of α = 0.05.The p-value is 0.026 (from LinRegTTest on your calculator or from computer software).Use the line to predict the final exam score (predicted y value)? Can the regression line be used for prediction? Given a third exam score ( x value), can we.The line of best fit is: ŷ = -173.51 + 4.83 x with r = 0.6631 and there are n = 11 data points.Consider the third exam/final exam example.THIRD-EXAM vs FINAL-EXAM EXAMPLE: p-value method In this chapter of this textbook, we will always use a significance level of 5%, α = 0.05 Method 2: Using a table of critical values.The two methods are equivalent and give the same result. There IS A SIGNIFICANT LINEAR RELATIONSHIP (correlation) between x and y in the population.ĭRAWING A CONCLUSION:There are two methods of making the decision. Alternate Hypothesis H a: The population correlation coefficient IS significantly DIFFERENT FROM zero.There IS NOT a significant linear relationship (correlation) between x and y in the population. Null Hypothesis H 0: The population correlation coefficient IS NOT significantly different from zero.If r is significant and if the scatter plot shows a linear trend, the line may NOT be appropriate or reliable for prediction OUTSIDE the domain of observed x values in the data.If r is not significant OR if the scatter plot does not show a linear trend, the line should not be used for prediction.Y for values of x that are within the domain of observed x values. If r is significant and the scatter plot shows a linear trend, the line can be used to predict the value of.Therefore, we CANNOT use the regression line to model a linear relationship between x and y in the population. What the conclusion means: There is not a significant linear relationship between x and y.Conclusion: "There is insufficient evidence to conclude that there is a significant linear relationship between x and y because the correlation coefficient is not significantly different from zero.".If the test concludes that the correlation coefficient is not significantly different from zero (it is close to zero), we say that correlation coefficient is "not significant". We can use the regression line to model the linear relationship between x and y in the population. What the conclusion means: There is a significant linear relationship between x and y.Conclusion: There is sufficient evidence to conclude that there is a significant linear relationship between x and y because the correlation coefficient is significantly different from zero.If the test concludes that the correlation coefficient is significantly different from zero, we say that the correlation coefficient is "significant." We decide this based on the sample correlation coefficient r and the sample size n. The hypothesis test lets us decide whether the value of the population correlation coefficient ρ is "close to zero" or "significantly different from zero". r = sample correlation coefficient (known calculated from sample data).ρ = population correlation coefficient (unknown).The symbol for the population correlation coefficient is ρ, the Greek letter "rho.".The sample correlation coefficient, r, is our estimate of the unknown population correlation coefficient. But because we have only sample data, we cannot calculate the population correlation coefficient. ![]() If we had data for the entire population, we could find the population correlation coefficient. The sample data are used to compute r, the correlation coefficient for the sample. We perform a hypothesis test of the "significance of the correlation coefficient" to decide whether the linear relationship in the sample data is strong enough to use to model the relationship in the population. We need to look at both the value of the correlation coefficient r and the sample size n, together. However, the reliability of the linear model also depends on how many observed data points are in the sample. The correlation coefficient, r, tells us about the strength and direction of the linear relationship between x and y.
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