Effects of Good Teachers on Student Outcomes

These findings would suggest that the difference in achievement gains between having a 25th percentile teacher (a not so effective teacher) and a 75th percentile teacher (an effective teacher) is over one-third of a standard deviation (0.35) in reading and almost half a standard deviation (0.48) in mathematics. Similarly, the difference in achievement gains between having a 50th percentile teacher (an average teacher) and a 90th percentile teacher (a very effective teacher) is about one-third...

 Correlation Between Perception of Birth and Maternal Infa...

As reported previously, the strongest influence on maternal infant bonding (MFA) in the regression analysis was a woman‘s perception of her birth experience (POBS) as revealed by an R-squared of 0.055, p < 0.01, which represents 5.5% of the proportion of variation in maternal infant bonding. Furthermore, the correlation analysis between POBS and MFA demonstrated a correlation of 0.234, p< 0.01. In addition, a notable finding was the POBS mean of 107.07 and SD of 18.92, which is a modera...

 The Importance of Large Samples

Any experiment may be regarded as forming an individual of a 'population' of experiments which might be performed under the same conditions. A series of experiments is a sample drawn from this population. Now any series of experiments is only of value in so far as it enables us to form a judgment as to the statistical constants of the population to which the experiments belong. In a great number of cases the question finally turns on the value of a mean, either directly, or as the mean diffe...