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# Tutor profile: Joshua S.

Joshua S.
MD, PhD - Experience tutoring for medical school, statistics, physics, neuroscience, biology

## Questions

### Subject:MCAT

TutorMe
Question:

Which of the following statements about the brain is FALSE? A. The pons functions to link the cerebellum with the higher conscious centers. B. The limbic system alerts the cortex of incoming stimuli. C. The limbic system is associated with emotional responses. D. The nuclei of cranial nerves 5, 6, 7, and 8 are located in the pons.

Joshua S.

(B). The limbic system includes the limbic lobe as well as the associated subcortical nuclei. It is associated with emotional responses and the integration of olfactory information with visceral and somatic information.

### Subject:Medicine

TutorMe
Question:

What is the difference between HFpEF and HFrEF, and how do you distinguish between them?

Joshua S.

HFpEF = Heart Failure with PRESERVED Ejection Fraction HFrEF = Heart Failure with REDUCED Ejection Fraction Distinguish between them using an echocardiogram to measure the patient's ejection fraction.

### Subject:Data Science

TutorMe
Question:

Suppose you have a large, two-dimensional data set. You try to separate the data into two groups. What statistical test could you perform to demonstrate that the two groups are statistically distinct?

Joshua S.

You can employ the F-test. The F-test employs calculation of the between-group variability in the numerator and the within-group variability in the denominator. Each group will be separated by a certain amount in two dimensions, which you can obtain by finding the mean difference (squared) between the mean of each group and the mean of all points together, and use this as the between-group variability. For the within-group variability, calculate the mean two-dimensional variance for all points within each group and add them together. Divide these numbers to obtain the F statistic. A large F corresponds to a greater degree of certainty that you have two distinct groups. To obtain a p-value, you'll need the number of degrees of freedom in the numerator and in the denominator. The numerator will have K - 1 d.o.f., where K is the number of groups, giving you 1 d.o.f. in the numerator. The denominator will have N - K d.o.f., where N is the total number of data points. Use these in a lookup table or appropriate software to match your calculated F and degrees of freedom to an appropriate p-value.

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