Suppose a cognitive neuropsychologist suspects that children with mild lead expo

Question

Suppose a cognitive neuropsychologist suspects that children with mild lead exposure have reading and writing challenges. She tests a sample of 81 children with mild lead exposure by testing performance on the Woodcock Johnson Reading Mastery Word Identification subset: mu for the test is 100. The cognitive neuropsychologist's sample scores an average of 97 with a standard deviation of 14.9. The null hypothesis is that children with mild lead exposure will score no lower on the identification subtest than the general population. Formulate this hypotheis test as: H_0: mu_lead lessthanorequalto mu_general population: H_1: m_lead > mu_general population H_0: mu_lead notequalto mu_general population: H_1: m_lead = mu_general population H_0: mu_lead = mu_general population: H_1: m_lead notequalto mu_general population H_0: mu_lead greaterthanorequalto mu_general population: H_1: m_lead

Explanation / Answer

The null hypothesis assumes that children with lead expose will score no lower than general population, which implies that children with lead exposure will score equal or might be higher than general population. Thus, the null hypothesis are as follows:

H0:mulead>=mugeneral population

The researcher wants to know whether children with mild lead exposure have reading and writing challenges, which implies, children with lead exposure will have lower score than general population. Thus, the alternative hypothesis is as follows:

H1:mulead< mugeneral population

This is a left-tailed test (the alternative hypothesis uses < sign).

The given level of significance is 0.01, and degrees of freedom for 1-sample t test is n-1, where, n is sample size. That is df=81-1=80.

The critical t(80) at alpha=0.01 is 2.37.

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