Hypothesis Testing: Wrong Critical Z Score Explained

[yelenaaa13]

 

[I like Serena]

It looks as if question (2) asks about a left sided hypothesis.
The critical z-value should then typically be $-1.645$.

Where did you get the test statistic z?
To reject the null hypothesis, we need that the test statistic z is more negative than $-1.645$.

In question (3) we have a 2-sided hypothesis.
It means that we need to find the critical z-value for $\frac \alpha 2=0.005$, which is $\pm 2.5758$.

 

[yelenaaa13]

It looks as if question (2) asks about a left sided hypothesis.
The critical z-value should then typically be $-1.645$.

Where did you get the test statistic z?
To reject the null hypothesis, we need that the test statistic z is more negative than $-1.645$.

What is your problem with question (3)?

Thank you for your response!

I got the test statistic from this formula: ((p-hat - p)/(square root((p(1-p))/n) ( i attached an image of the formula i used since this is kind of hard to read).
It was cut off, but p-hat and n were given. p-hat is 0.75 and n = 90.

And my problem with question 3 is the z critical values. It says 2.33 and -2.33 are wrong, but on the table those are the values that correspond with an alpha of 0.01

 

[I like Serena]

And my problem with question 3 is the z critical values. It says 2.33 and -2.33 are wrong, but on the table those are the values that correspond with an alpha of 0.01

Question 3 has a 2-sided hypothesis. We need the values that correspond to alpha/2=0.005.

Question 2 has a left-sided hypothesis. You probably need a minus sign in front of the critical z-value.

 

[yelenaaa13]

Question 3 has a 2-sided hypothesis. We need the values that correspond to alpha/2=0..005.

Question 2 has a left-sided hypothesis. You probably need a minus sign in front of the critical z-value.

Okay that's exactly what was wrong. Thank you so much for your help!