Tuppence writes:
The results of the rotating mirror experiments are summarized in Table 6. If the results rejected by the experimenters themselves are omitted along with Fourcault’s admittedly pioneer experiment which was “intended to ascertain the possibilities of the method,” then a least squares linear fit to the six data points gives a decay of 1.85 Km/s per year. The value of the correlation coefficient, r, equals -0.932, with a confidence interval of 99.6% in this decay correlation.
But what is the value of chi Squared? That is essential. The value of chi squared will help us answer the question of whether the data actually fit a linear model. Hogh correlation coefficients are nice, but they don't help us here. The correlation coefficient is a measure of how closely the data fit a (linear, in this case) model given that they actually fit a linear model. Similarly, the value of the slope of the line of best fit is of interest only if the data actually fit a linear model. We need chi squared to answer that threshold question.