# Tutor profile: Winny N.

## Questions

### Subject: Psychology

What is the main change from DSM IV TR to DSM 5 for Schizophrenia? What are the differences between Brief Psychotic Disorder, Schizophreniform, Schizophrenia and Schizoaffective?

In the DSM IV TR, Schizophrenia was divided into many different sub-types. For the new DSM 5, they collapsed all the sub-types into 1 category. Brief Psychotic Disorder has a sudden onset of at least 1 psychotic symptom (delusion, hallucination, disorganized speech, grossly disorganized or catatonic behaviour) and can last from 1 day to 1 month. Schizophreniform is longer, lasting from 1-6 months and is a pre-morbid condition to Schizophrenia. For the diagnosis of Schizophrenia, symptoms must be present for at least 6 months. Schizoaffective is when someone has both Schizophrenia AND a Mood Disorder (like Depression).

### Subject: Biology

How do action potentials work?

The human brain consists of around 100 billion neurons, communicating with each other through action potentials. The action potential can be divided into different stages. Stage 1: Resting Membrane Potential (RMP) At rest (without any stimulus), the neuron stays at a constant resting membrane potential of -70 mV. The RMP is established by the Na+/K+ pump, creating a low concentration of sodium inside the cell and a high concentration of potassium ions inside the cell. Stage 2: Depolarization If you reach threshold, voltage-gated sodium channels open, allowing a large influx of Na+ ions INSIDE the cell. This causes the membrane potential to increase (becomes more positive). Stage 3: Peak At the peak of the action potential, the voltage-gated sodium channels become inactivated and does not allow sodium ions to enter the cell. Stage 4: Repolarization Voltage-gated Na+ channels close, while voltage-gated K+ channels open, resulting in a large efflux of K+ ions. This means that K+ ions are moving OUT of the cell and the membrane potential starts to decrease (becomes more negative). Stage 5: Hyperpolarization At this stage, voltage-gated K+ channels close and the membrane potential returns back to RMP.

### Subject: Statistics

In 1997, 46% of Americans said they did not trust the media when it comes to reporting the news fully, accurately and fairly. In a 2007 poll of 1010 adults nationwide, 525 stated they did not trust the media. At the alpha = 0.05 level of significance, is there evidence to support the claim that the percentage of Americans that do not trust the media to report fully and accurately has increased since 1997?

This question involves hypothesis testing about a population proportion and we want to know if p > p (initial) = 0.46. Step 1: Define the null hypothesis (H0) and alternative hypothesis (H1). The null hypothesis always assumes that there is no significant difference between the two values. In this example, H0: p = p (initial) = 0.46, whereas H1: p>0.46. Step 2: What is the level of significance required? Alpha = 0.05 Step 3: What is the sample proportion? p = 525/1010 = 0.52 Step 4: Calculate the observed value of the test statistic. [{z_0} = \frac{{p - {p_{initial}}}}{{\sqrt {{p_{initial}}(1 - {p_{initial}})/n} }} = \frac{{0.52 - 0.46}}{{\sqrt {\frac{{0.46(1 - 0.46)}}{{1010}}} }} = 3.83\] Step 5: Since we have a right-tailed test, we determine the critical value at the alpha = 0.05 level of significance to be z = 1.645 (critical value is taken from the Table) Step 6: Since the observed value z initial = 3.83 and 3.83 > 1.645, we must reject the null hypothesis. Step 7: There is sufficient evidence at the alpha = 0.05 level of significance to conclude that the percentage of Americans that do not trust the media to report fully and accurately has increased since 1997.

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