statistics Flashcards
The scientists carried out a statistical test to see if the difference in the distribution of each species between the canopy and understorey was due to chance. The P values obtained are shown in the table.
(zaretys itys has a p value > 0.05
and the rest of the species all hav a p value of < 0.001)
Explain what the results of these statistical tests show.
The scientists carried out a statistical test to see if the difference in the distribution of each species between the canopy and understorey was due to chance. The P values obtained are shown in the table.
(zaretys itys has a p value > 0.05
and the rest of the species all hav a p value of < 0.001)
Explain what the results of these statistical tests show.
For Zaretis itys, difference in distribution is probably due to chance
for the rest of the species, difference in distribution is unlikely due to chance
because < 0.001, which is highly significant
In an investigation, cyanogenic and acyanogenic plants were grown together in pots. Slugs were placed in each pot and records were kept of the number of leaves damaged by the feeding of the slugs over a period of 7 days. The results are shown in Table 1.
a x^2 test was carried out
state the null hypothesis
x^2 was calculated and it was to correspond to a probability of less than 0,05. what conclusion can you draw from this?
In an investigation, cyanogenic and acyanogenic plants were grown together in pots. Slugs were placed in each pot and records were kept of the number of leaves damaged by the feeding of the slugs over a period of 7 days. The results are shown in Table 1.
a x^2 test was carried out
state the null hypothesis
there was no diff between damage in cyanogenic and acyanogenic plants
x^2 was calculated and it was to correspond to a probability of less than 0,05. what conclusion can you draw from this?
(accept/reject)we reject the null hypothesis,
(significance)there is a significant difference between damage in cyanogenic and acyanogenic plants
(conclusion)being cyanogenic does help plants from slug damage
The doctors carried out a statistical test to determine whether the antibody concentrations were significantly different in girls given two doses of the vaccine, compared with those given three doses. They determined the mean concentrations of antibody 9 months after the first dose of vaccine.
What statistical test should the doctors have used? Give the reason for your choice.
t test
because comparing two means
Describe briefly how you would use a statistical test to find whether there is a significant correlation between mean March temperature and the date when chaffinches laid their first egg.
Describe briefly how you would use a statistical test to find whether there is a significant correlation between mean March temperature and the date when chaffinches laid their first egg.
construct null hypothesis use spearman rank and calc test statistic look up in table (to find cv of p = 0.05) use figure (in table) to accept or reject null hypothesis
Scientists found that there was a correlation between mean annual temperature
and the date when chaffinches laid the first egg. Can you conclude that higher
temperatures cause earlier laying of the first egg?
Explain your answer.
Scientists found that there was a correlation between mean annual temperature
and the date when chaffinches laid the first egg. Can you conclude that higher
temperatures cause earlier laying of the first egg?
Explain your answer.
A correlation does not indicate a causal relationship;
As may be due to another factor
The inheritance of body colour in fruit flies was investigated. Two fruit flies with grey
bodies were crossed. Of the offspring, 152 had grey bodies and 48 had black bodies.
(b) Explain why a statistical test should be applied to the data obtained in this
investigation.
The inheritance of body colour in fruit flies was investigated. Two fruit flies with grey
bodies were crossed. Of the offspring, 152 had grey bodies and 48 had black bodies.
(b) Explain why a statistical test should be applied to the data obtained in this
investigation.
to determine the probability of the results being due to chance
A medical officer investigated the effectiveness of five different types of influenza vaccine.
A total of 1350 people agreed to be vaccinated. The medical officer divided these into five
groups. The number who suffered from influenza in the following year was recorded. The
results are shown in the table.
suffered didn’t suffer total proportiosuffering
I 43 237 280 0.15
II 52 198 250 0.21
III 25 245 270 0.09
IV x y 260 0.18
V 57 233 290 0.20
(a) Complete the spaces in the table for the people vaccinated with type IV vaccine.
(b) The medical officer used a statistical test to assess the effectiveness of the five different vaccines.
(i) What would be the null hypothesis?
(ii) The statistical test gave a probability of less than 0.05. What conclusion can be drawn from this?
A medical officer investigated the effectiveness of five different types of influenza vaccine.
A total of 1350 people agreed to be vaccinated. The medical officer divided these into five
groups. The number who suffered from influenza in the following year was recorded. The
results are shown in the table.
suffered didn’t suffer total proportiosuffering
I 43 237 280 0.15
II 52 198 250 0.21
III 25 245 270 0.09
IV x y 260 0.18
V 57 233 290 0.20
(a) Complete the spaces in the table for the people vaccinated with type IV vaccine.
x = 47
y = 213
(b) The medical officer used a statistical test to assess the effectiveness of the five different vaccines.
(i) What would be the null hypothesis?
there is no significant difference between the effectiveness of the five different influenza vaccines
(ii) The statistical test gave a probability of less than 0.05. What conclusion can be drawn from this?
(accept/reject)we reject the null hypothesis,
(significant) there is a significant difference between the effectiveness of the different types of vaccines
A student investigated whether the abundance of the orange star lichen on the walls of a
building was influenced by the direction the wall faced. The student recorded the number
of colonies within a 50 cm2 quadrat, placed one metre above the ground on each of three
walls.
A X^2 test was applied to the results.
(a) Give a null hypothesis for this investigation.
A student investigated whether the abundance of the orange star lichen on the walls of a
building was influenced by the direction the wall faced. The student recorded the number
of colonies within a 50 cm2 quadrat, placed one metre above the ground on each of three
walls.
A 2
test was applied to the results.
(a) Give a null hypothesis for this investigation.
there is no SIGNIFICANT difference between the abundance of lichens growing on the walls
df (degrees of freedom) of chi squared
n-1
df (t test)
( Na + Nb ) - 2
df (spearman rank)
n - 2
Complete the following table.
Number of colonies on a wall facing
North South West Observed 21 33 54 Expected
Complete the following table.
Number of colonies on a wall facing
North South West Observed 21 33 54 Expected 36 36 36
A x^2 value of 15.5 was calculated from these results. This x^2 value has a
probability of less than 0.001. Explain what this means when applied to this
investigation.
A 2 value of 15.5 was calculated from these results. This 2 value has a
probability of less than 0.001. Explain what this means when applied to this
investigation.
p less than 0.05 so reject the null hypothesis;
there is a significant difference;
the direction the wall faces does have an effect on the population of lichens;
The diagram shows a seahorse. A seahorse is a fish.
The scientists measured the head lengths of the female and male of a number of pairs.
(d) The scientists concluded that total body length affects the selection of a mate.
Explain how the results support this conclusion.
The diagram shows a seahorse. A seahorse is a fish.
The scientists measured the head lengths of the female and male of a number of pairs.
(d) The scientists concluded that total body length affects the selection of a mate.
Explain how the results support this conclusion.
positive correlation between head length of male and females
p > 0.05 we ____ null
p < 0.05 we _____ null
p > 0.05 we accept null
p< 0.05 we reject null
