Data Analysis workshop/Jan 28

My research hypothesis: Emersion DOES NOT slow growth for Nucella Lamallosa.

My statistical null hypothesis: Emersion DOES slow growth for Nucella Lamallosa because snails need to be in the water to grow their shells.

The P-value is more than alpha, so I fail to reject the statistical null hypothesis.

1. What do the measures of central tendency tell us? A dimension is identified and a reference point is chosen, and measurement of distance to the center of the distribution is from that reference point. They are the mean, median, and mode, that under the bell curve all are equal.

2. When is each appropriate?

a. The mean is the average. This is good to use to get a better idea when there is data skewed.

b. The median does refer to the number in the middle. Use if there are extremely high or extremely low values in the data set.

c. The mode of a data set refers to the number that occurs most often. When you have categorical data, or data that appears as words instead of numbers, you need to use the mode.

3. What do the measures of variability (dispersion) tell us? Variance is the average squared deviation from the population mean. The variance is a number which tells us about the distance of the numbers from the central mean. The standard deviation (or the square root of the variance) as an average variability of the numbers around the mean. It shows relationships between two things. Standard Deviation Error is for one thing.

4. When is each appropriate? Standard Deviation Error is to be used when you don’t have replicants.

5. What does it mean to be one standard deviation away from the mean? 68% of the data falls into one deviation.

6. What does it mean to be two standard deviations away from the mean? 95% of the data falls into one deviation.

7. Why do we need to look at both central tendency and variability? Between the two you get a better picture.

What do error bars mean? They give a level of confidence in a certain range. If 95% CI error bars do not overlap, you can be sure the difference is statistically significant (P <>

8. What is a level of significance ()? It’s where we choose our level of cut-off for distinguishing between a true signal and chance.

9. How do we choose it? This is an arbitrary choice. The standard is 0.05.

10. What is a P-value? This is the probability that your statistical null hypothesis is correct.

11. How do you interpret the P-value in plain English? You say, “There is a XX% probability due to chance.”

12. What is the null hypothesis of the t-test? The null hypothesis of the t-test says that the two means are the same.

13. How can a research hypothesis and a statistical null hypothesis differ? The null hypothesis typically proposes a general or default position. Research hypothesis testing is used to decide whether the data contradicts the null hypothesis.

14. Are they always different? Yes

15. Why? They are opposites of each other.

16. What is the difference between a one- and two-tailed test? They are both the concept of directionality. A one-tailed test is directional. A two-tailed test does not specify a direction. The test is designed so that the criteria uses both the upper and lower part of a distribution.