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# Tutor profile: Costa K.

Costa K.
Experienced Math and Statistics teacher/tutor for 15 years.

## Questions

### Subject:Pre-Calculus

TutorMe
Question:

When $$\log f(x)=0$$, what can you say about the function $$f(x)$$?

Costa K.

The function is equal to the constant function $$f(x)=1$$.

### Subject:Calculus

TutorMe
Question:

Does a function $$f(x)$$ have local minimum or local maximum at $$\alpha$$ when its derivative is zero ?

Costa K.

When the derivative of a function $$f(x)$$ is zero, the function may have a local minimum or local maximum or in some cases a "turning" point.

### Subject:Statistics

TutorMe
Question:

When do we calculate the z statistic versus the t statistic from a given sample of size n?

Costa K.

When the standard deviation of the population is given, then we use the z statistic.

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