The times for untrained rats to run a standard maze has a N (65, 15) distribution where the times are measured in seconds. The researchers hope to show that training improves the times. The alternative hypothesis is
a. Ha: 碌 %26gt; 65.
b. Ha: %26gt; 65.
c. Ha: 碌 %26lt; 65.|||You want to improve the times, so we are looking or a smaller length of time for training. the alternate hypothesis is:
c. Ha: 碌 %26lt; 65.
== -- == -- ==
Consider the hypothesis as a trial against the null hypothesis. the data is evidence against the mean. you assume the mean is true and try to prove that it is not true. After finding the test statistic and p-value, if the p-value is less than or equal to the significance level of the test we reject the null and conclude the alternate hypothesis is true. If the p-value is greater than the significance level then we fail to reject the null hypothesis and conclude it is plausible. Note that we cannot conclude the null hypothesis is true, just that it is plausible.
If the question statement asks you to determine if there is a difference between the statistic and a value, then you have a two tail test, the null hypothesis, for example, would be 渭 = d vs the alternate hypothesis 渭 鈮?d
if the question ask to test for an inequality you make sure that your results will be worth while. for example. say you have a steel bar that will be used in a construction project. if the bar can support a load of 100,000 psi then you'll use the bar, if it cannot then you will not use the bar.
if the null was 渭 鈮?100,000 vs the alternate 渭 %26lt; 100,000 then will will have a meaningless test. in this case if you reject the null hypothesis you will conclude that the alternate hypothesis is true and the mean load the bar can support is less than 100,000 psi and you will not be able to use the bar. However, if you fail to reject the null then you will conclude it is plausible the mean is greater than or equal to 100,000. You cannot ever conclude that the null is true. as a result you should not use the bar because you do not have proof that the mean strength is high enough.
if the null was 渭 鈮?100,000 vs. the alternate 渭 %26gt; 100,000 and you reject the null then you conclude the alternate is true and the bar is strong enough; if you fail to reject it is plausible the bar is not strong enough, so you don't use it. in this case you have a meaningful result.
Any time you are defining the hypothesis test you need to consider whether or not the results will be meaningful.|||c (we want the times to be faster ie less than 65seconds)|||a. Ha: 碌 %26gt; 65.
Thursday, December 15, 2011
Statistics: null hypothesis & alternative hypothesis?
I'm having trouble with understanding null %26amp; alternative hypothesis. Here is the question:
A poll of 1,068 adult Americans reveal that 48.0% of the voters surveyed prefer the Democratic candidate for the presidency. At the 0.05 level of significance, test the claim that at least half of all voters prefer the Democrat.
A) Put the claim in symbolic form. Does the claim include equality?
B) State the null hypothesis and the alternative hypothesis.|||Null: p%26lt;.50, Alternate: p%26gt;.50 (this should be a "p is greater OR EQUAL to .5)
The claim is the alternate hypothesis. If it involves an inequality, the equal sign will always go with the alternate. In other words, once you figure out the equations, you will automatically know which one is the alternate, because it will have two signs (in this case, a 'greater than' sign and an 'equal' sign).
A poll of 1,068 adult Americans reveal that 48.0% of the voters surveyed prefer the Democratic candidate for the presidency. At the 0.05 level of significance, test the claim that at least half of all voters prefer the Democrat.
A) Put the claim in symbolic form. Does the claim include equality?
B) State the null hypothesis and the alternative hypothesis.|||Null: p%26lt;.50, Alternate: p%26gt;.50 (this should be a "p is greater OR EQUAL to .5)
The claim is the alternate hypothesis. If it involves an inequality, the equal sign will always go with the alternate. In other words, once you figure out the equations, you will automatically know which one is the alternate, because it will have two signs (in this case, a 'greater than' sign and an 'equal' sign).
The alternative hypothesis?
The alternative hypothesis
A. Tells the value of the sample mean
B. None of these
C. Will always contain the equal sign
D. Is accepted if the null hypothesis is rejected|||D
[if] The null hypothesis is rejected IN FAVOUR of the alternative hypothesis
A. Tells the value of the sample mean
B. None of these
C. Will always contain the equal sign
D. Is accepted if the null hypothesis is rejected|||D
[if] The null hypothesis is rejected IN FAVOUR of the alternative hypothesis
Statistics-Null and Alternative hypothesis! HELP!!?
Generally it is assumed that female students have higher GPA鈥檚 than male students. Thus, I decided to test this common assumption. (Gender vs. GPA)
Using this information, can anyone please answer these quick questions:
State the hypothesis
Write out the null hypothesis
Write out the alternative hypothesis
THANKS YOU!!!|||State the hypothesis
female students have higher GPA鈥檚 than male students.
null hypothesis : No difference in GPA between males and females
alternative hypothesis : female students have higher GPA鈥檚 than male students
Using this information, can anyone please answer these quick questions:
State the hypothesis
Write out the null hypothesis
Write out the alternative hypothesis
THANKS YOU!!!|||State the hypothesis
female students have higher GPA鈥檚 than male students.
null hypothesis : No difference in GPA between males and females
alternative hypothesis : female students have higher GPA鈥檚 than male students
What hypothesis has been presented as an alternative to both the Hunting Hypothesis and the Gathering Hypothes?
It sounds like the question is saying that our ancestors survived by doing something other than hunting food and gathering food.
The only alternative to those would be foraging at the edge of large bodies of water, with limited fishing. I however would count both as types of gathering and hunting, respectively.
I have never heard of an alternative hypothesis to either method of food acquisition.|||Ranching and farming are the modern alternatives to hunting and gathering.
A few people still go bird or deer hunting, and we have those odd mushroom hunters, but for the most part we don't do it anymore.
Man is an animal. All animals are in a constant search for food. If they're tracking an animal, it's called hunting. If they see a blackberry along the way and eat it, it's called gathering. Eventually we realized that we could raise animals and food and not have to go looking for it.
The only alternative to those would be foraging at the edge of large bodies of water, with limited fishing. I however would count both as types of gathering and hunting, respectively.
I have never heard of an alternative hypothesis to either method of food acquisition.|||Ranching and farming are the modern alternatives to hunting and gathering.
A few people still go bird or deer hunting, and we have those odd mushroom hunters, but for the most part we don't do it anymore.
Man is an animal. All animals are in a constant search for food. If they're tracking an animal, it's called hunting. If they see a blackberry along the way and eat it, it's called gathering. Eventually we realized that we could raise animals and food and not have to go looking for it.
Is 'The probability of rolling a 3 with a dice is 1/6' a null hypothesis or an alternative hypothesis?
In theory, it is an alternative hypothesis, where to get any number on a die by rolling, it is 1 / 6.
In reality, the probability changes each time you roll, so it is a null hypothesis.|||It depends on what you want to show. If you want to show the die to be biased to have lower or higher probability of a 3 than 1/6, the assumption that it is fair will be the null hypothesis.
Generally, if you want to show that a certain theory holds, you make the inverse of the theory the null hypothesis, and show that, given the evidence, this is so unlikely that you have high confidence that your theory holds.|||It can be either.
If you want to test if the die is unbiased:
H0: prob of 3 = 1/6 --- null
H1: it is not 1/6 --- alternative
If you suspect that the die is biased and want to know that 3 has a probability of 2/3, then the following can be null and alternative hypotheses.
H0: prob of 3 = 2/3
H1: prob of 3 = 1/6
In reality, the probability changes each time you roll, so it is a null hypothesis.|||It depends on what you want to show. If you want to show the die to be biased to have lower or higher probability of a 3 than 1/6, the assumption that it is fair will be the null hypothesis.
Generally, if you want to show that a certain theory holds, you make the inverse of the theory the null hypothesis, and show that, given the evidence, this is so unlikely that you have high confidence that your theory holds.|||It can be either.
If you want to test if the die is unbiased:
H0: prob of 3 = 1/6 --- null
H1: it is not 1/6 --- alternative
If you suspect that the die is biased and want to know that 3 has a probability of 2/3, then the following can be null and alternative hypotheses.
H0: prob of 3 = 2/3
H1: prob of 3 = 1/6
Why are null and alternative hypothesis mutually exclusive?
They have to be by definition. One is the assumed hypothesis (null) and the other is an alternate (what is true if the null hypothesis isn't). By the very definition of the terms, they can't both be true. So H0: X= N goes with the alternatve H1: X IS NOT EQUAL to N.|||if they were'nt the experimental design would be impossible how can we have h0: there was no variance attributable to the treatment condition AND say hA: there is variance due to treatment condition AND have both be simultaneously true its like saying "the next sentence is true. The preceding sentence was false"
get my drift???
get my drift???
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