Question

Part 1)

Imagine we conduct a study to determine how long it takes salesclerks to approach and help hearing-disabled customers. If differences do emerge between these two IV levels, can we say confidently that the differences are due to deafness, or might there be another variable at play (like chance) that better accounts for any observed differences? Think of two factors that account for why helping times might differ between conditions (other than deafness vs. hearing)

Part 2)

Why is it important that the tails of a normal curve never touch the X-axis? You tell me!

Answer 1

Hearing disabled person is accompanied by a guardian is one of the factor and the other is the degree of deafness and definitely depends upon the skills of the sales person to help them through hand movements or by writing if the person can read

2)
Because on a perfectly normal distribution, every event number on the horizontal-axis has at least some probability of happening, no matter how small it is. If it had a probability of 0, then it wouldn't be part of a standard normal distribution.

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