Question

Without external cues such as the sun, people attempting to walk in a straight line tend to walk in circles. It has been suggested that this tendency is due to internal asymmetries between individuals, or that individuals' legs differ in length or strength.

Souman et al. (2009) tested for differences in individuals' tendencies to change direction by blindfolding 15 participants and asking them to walk in a straight line in an empty field. The numbers in this dataset represent median change in direction (or turning angle) of each of the 15 participants, measured in degrees per second. Negative angles = left turns; positive angles = right turns.

Begin by producing a frequency distribution graph of the dataset for yourself.

-5.19
-1.2
-0.5
-0.33
-0.15
-0.15
-0.15
-0.07
0.02
0.02
0.28
0.37
0.45
1.76
2.8

1. Do the data appear to be normally distributed? Answer "yes" or "no"
2. Based on the graph, do people tend to turn in one direction more than the other? Answer "right" or "left"
3. Is this a 1- or a 2-tailed t test?  (enter either "1" or "2" for your answer)
4. Conduct a one-sample t-test. What is your calculated t-value? Answer to 2 decimal places, and include leading zeros:
5. Does the mean angle differ significantly from zero? "yes" / "no"
6. Based on your test, is the following statement justified? "People do not have a tendency to turn more in one direction, on average, than the other direction." "yes" / "no"
   

Answer 1

a) Normal Assessment:

Ryan-Joiner Test
Test statistic, Rp: 0.8547
Critical value for 0.05 significance level: 0.938
Critical value for 0.01 significance level: 0.91
Reject normality with a 0.05 significance level.

b) We histogram from the given data

The histogram shows that the data is negative skewed distribution i.e. left skewed distribution.

c) It is 2-tailed t test

d) From the given data

No, the mean angle not differ significantly from zero

Yes, Based on your test, is the following statement justified? "People do not have a tendency to turn more in one direction, on average, than the other direction."