The target thickness for silicon wafers used in a certain type of integrated circuit is 245 µm. A sample of 50 wafers is obtained and the thickness of each one is determined, resulting in a sample mean thickness of 246.18 µm and a sample standard deviation of 3.60 µm. Does this data suggest that true average wafer thickness is something other than the target value?

An article shows data to compare several methods for predicting the shear strength for steel plate girders. Data for two of these methods, the Karlsruhe and Lehigh procedures, when applied nine times to a girder, are shown in the following table. We wish to determine whether there is any difference between the two methods. Assume the same standard deviations. (Note that we will perform unpaired comparison. We do not perform a paired test.) Karlsruhe Method Lehigh Method 1.21304 1.160384 1.251478 1.268834 1.218271 1.214254 1.232497 1.244961 1.142573 1.091621 1.286563 1.2297 1.239222 1.219269 1.161394 1.162844 1.169785 1.118203 1.231058 1.199258 1.233329 1.269486 1.153381 1.106666 1.2. For a sample standard deviation, use Excel function STDEV.S(), not STDEV.P(). Fill in the blanks below: Karlsruhe Method Lehigh Method x1 = x2 = s1 = s2 = n1 = n2 =   1.3. Do the data suggest that the two…

The National Weather Service says that the mean daily high temperature for October in a large mid-western city is 56°F. A local weather service suspects that this value is not accurate and wants to perform a hypothesis test to determine whether the mean is actually lower than 56°F. A sample of mean daily high temperatures for October over the past 37 years yields a sample mean of 54o F. Assume that the population standard deviation is 5.6° F. Perform the hypothesis test at the 1% significance level. STEP 1. H0: µ:____   ______o   _____: H1: µ ____  o         NOTE: For ≠ enter /= STEP 2. This test is (e) left-tailed, (f) two-tailed or (g) right-tailed test. This test is:___  (enter e, f or g) STEP 3. The critical value (s) is Use the following chart to identify the critical value (s)                            Left-tailed                         Two-tailed                                         Right tailed α =10%           z = -1.28 (A)                     z=∓1.65 (B)…

The void volume within a textile fabric affects comfort, flammability, and insulation properties. Permeability of a fabric refers to the accessibility of void space to the flow of a gas or liquid. An article gave summary information on air permeability (cm3/cm2/sec) for a number of different fabric types. Consider the following data on two different types of plain-weave fabric: Fabric Type Sample Size Sample Mean Sample Standard Deviation Cotton 10 51.41     0.75 Triacetate 10 132.15     3.59 Assuming that the porosity distributions for both types of fabric are normal, let's calculate a confidence interval for the difference between true average porosity for the cotton fabric and that for the acetate fabric, using a 95% confidence level. Before the appropriate t critical value can be selected, df must be determined: df =    0.5625 10  +  12.8881 10   2   (0.5625/10)2 9  +  (12.8881/10)2 9  =  1.8092 0.1849…

A lumber company is making boards that are 2900 millimeters tall. If the boards are too long they must be trimmed, and if they are too short they cannot be used. A sample of 35 boards is taken, and it is found that they have a mean of 2900.3 millimeters. Assume a population standard deviation of 8. Is there evidence at the 0.01 level that the boards are either too long or too short?   Step 2 of 3 :   Find the P-value for the hypothesis test. Round your answer to four decimal places.

The slant shear test is widely accepted for evaluating the bond of resinous repair materials to concrete; it utilizes cylinder specimens made of two identical halves bonded at 30°. An article reported that for 12 specimens prepared using wire-brushing, the sample mean shear strength (N/mm2) and sample standard deviation were 18.60 and 1.56, respectively, whereas for 12 hand-chiseled specimens, the corresponding values were 23.19 and 4.07. Does the true average strength appear to be different for the two methods of surface preparation?   State and test the relevant hypotheses using a significance level of 0.05. (Use ?1 for wire-brushing and ?2 for hand-chiseling.) H0: ?1 − ?2 = 0Ha: ?1 − ?2 ≤ 0H0: ?1 − ?2 = 0Ha: ?1 − ?2 < 0    H0: ?1 − ?2 = 0Ha: ?1 − ?2 > 0H0: ?1 − ?2 = 0Ha: ?1 − ?2 ≠ 0 Calculate the test statistic and determine the P-value. (Round your test statistic to one decimal place and your P-value to three decimal places.) t  =    P-value  =   You may have computed…

2. Traces of toxic, man-made hexachlorohexanes in North Sea sediments were extracted by a known process and by two new procedures, and measured by chromatography. Method Concentration found Conventional Procedure A (pg/g) 34.4 42.9 Standard deviation (pg/g) 3.6 1.2 Number of replications 6 6 a.) Is the standard deviation for procedure A significantly different from that of the conventional procedure at 95% confidence level? b.) Is the mean concentration found by procedure A significantly different from that of the conventional procedure at 95% confidence level?