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Q59Section C (Section C)59 of 60

Width of a t confidence interval

Suppose that the weights (in kgs) of six months old babies, monitored at a healthcare facility, have N(μ,σ2)N(\mu,\sigma^2) distribution, where μ∈R\mu\in\mathbb{R} and σ>0\sigma>0 are unknown parameters. Let X1,X2,…,X9X_1,X_2,…,X_9 be a random sample of the weights of such babies. Let Xˉ=19∑i=19Xi\bar X=\frac19\sum_{i=1}^9 X_i, S=18∑i=19(Xi−Xˉ)2S=\sqrt{\frac18\sum_{i=1}^9(X_i-\bar X)^2} and let a 95%95\% confidence interval for μ\mu based on tt-distribution be of the form (Xˉ−h(S),Xˉ+h(S))(\bar X-h(S),\bar X+h(S)), for an appropriate function hh of random variable SS. If the observed values of Xˉ\bar X and S2S^2 are 99 and 9.59.5, respectively, then the width of the confidence interval is equal to __________ (round off to 2 decimal places) (You may use t9,0.025=2.262t_{9,0.025}=2.262, t8,0.025=2.306t_{8,0.025}=2.306, t9,0.05=1.833t_{9,0.05}=1.833, t8,0.05=1.86t_{8,0.05}=1.86)

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