Ascience teacher gives a test with 15 questions. this teacher is a hard grader. the teacher assigns points in the following manner: a correct answer =+1 point, an incorrect answer =−1 point, no answer =0 points. so scores on the test could range from +15 to −15. the teacher’s assistant calculates the standard deviation for scores on the test and reports sd =−2.3. what do we know?
- the standard deviation was calculated incorrectly.
- most students received negative scores.
- most students scored below the mean.
- there is an outlier that has a negative value close to -15.

 The standard deviation was calculated incorrectly.

Step-by-step explanation:

It cannot be negative , because it is the square root of the variance .

We add all squared deviations from the data points away from the mean and (then divide it by the number of data values) to evaluate variance.

Since , any squared number cannot give a negative result.

⇒ Standard deviation cannot be negative.

⇒The standard deviation was calculated incorrectly.

Rest other things (given in options) can not be interpreted on the basis of given information.

16

step-by-step explanation:

2 x 40 = 80

80/5

= 16

correct

step-by-step explanation: