151-4.docx

# 151-4.docx - 1 an observational study Can the data be...

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1 an observational study Can the data be generalized to a broader population ? No, The mothers were 94 healthy volunteers of similar age If infants born to smoking mothers in the study turned out to have lower birth weight than those born to non-smoking mothers, could this be used as proof that smoking lowers birth weight. No, because it is not appropriate for cause and effect inference. 2a 2b Center: HS<MS<NS Spreads: MS > HS > NS HS symmetric, MS skewed, NS symmetric There are no outliers.

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3a Summary statistics for WEIGHT: Group by: SMOKING SMOKING Mean Std. dev. Media n IQR HS 2764.8889 274.6476 2737367.5 MS 3013.3158396.29759 2934 671 NS 3534.6154248.59644 3531 320 3b Summary statistics for WEIGHT: Group by: SMOKING SMOKING Mean Std. dev. Media n IQR 80th Per. HS 2764.8889 274.6476 2737367.5 3036 MS 3013.3158396.29759 2934 671 3378 NS 3534.6154248.59644 3531 320 3753 For the infants in HS, 80 percent of them weight less than 3036 grams. ….. 4a One sample T confidence interval: Group by: SMOKING μ : Mean of WEIGHT 95% confidence interval results: SMOKING Sample Mean Std. Err. DF L. Limit U. Limit HS 2764.888945.774599 352671.96152857.8163 MS 3013.315890.916904 182822.30653204.3251 NS 3534.615439.807289 383454.0297 3615.201 Which interval is the widest 185.8547,382.0186, 161.1713
HS and MS overlaps, but they don’t overlap with NS. 4b One sample T hypothesis test: Where: SMOKING="MS" or "HS" μ : Mean of variable H 0 : μ = 3000 H A : μ < 3000 Hypothesis test results: Variable Sample Mean Std. Err. DF T-Stat P-value WEIGHT 3013.315890.916904 180.1464611 0.5574 State the null and alternative hypotheses H 0 : μ = 3000 H A : μ < 3000 Specify the distribution of the test statistic under the null hypothesis: T distribution df=18 the value of the test statistic 0.1464611 and the p-value of the test 0.5574 p-value = 0.5574, significance level = 0.05, p-value> significance level, don’t reject H0,

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• Winter '16
• Cristian Ivanescu
• Statistics, Statistical hypothesis testing, 80 percent, 3000 G, 3036 grams

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