COMPARISON OF PROJECTIVE MAPPING AND SORTING DATA COLLECTION AND MULTIVARIATE METHODOLOGIES FOR IDENTIFICATION OF SIMILARITY-OF-USE OF SNACK BARS1

Three data collection procedures, sorting and two forms of projective mapping (PM), were compared for ease-of-use and the ability to produce meaningful spatial maps when analyzed using Multidimensional Scaling (MDS), Generalized Procrustes Analysis (GPA) or Coordinate Averaging (CA). Eighteen commercially available snack bars were evaluated for similarity-of-use by two panels of 24. MDS of the sorting data and Procrustes analyses of PM data collected on unlabeled axis grouped the bars according to function and provided a meaningful spatial relationship in one dimension. However, MDS analysis of these PM data grouped the bars by similarity-of-use and provided a meaningful spatial interpretation in two dimensions. The CA analysis was not effective in separating the bars by similarity-of-use but did provide an indication of liking. A comparison of spatial configurations using RV coefficients showed moderate correlations between the methods. A panelist survey showed no significant differences in the ease-of-use, task interest or level-of-satisfaction with the final arrangement between the sorting and the PM data collection methods, but panelists did find it easier to change their minds using the PM procedure.     

THE DESIGN OF REPLICATED DIFFERENCE TESTS

We show that adding replications in replicated difference tests results in larger power and smaller variance when the number of assessors is fixed. On the other hand, when the number of total assessments is fixed, the power usually decreases and the variability increases whenever replications are considered instead of different assessors. The appropriate numbers of assessor needed to gain the same power and variability, respectively, when replications are used will be given. It is shown that the number of assessors might indeed be reduced, but this has to be paid for by an increasing total number of assessments. We show that two key models, namely the mixture binomial and a corrected version of the Beta-binomial model, are quite similar with respect to the properties of interest. We provide tables from which, according to her/his requirements, the investigator might find an appropriate setting with respect to the number of assessors and replications.     

COMPARISON OF CORRELATED PROPORTIONS IN REPLICATED PRODUCT TESTS

Product testing with multiple matched samples is often encountered. If the response for each sample is binary, the test involves comparison of multiple proportions of dependent samples. In the paper, a test statistic due to Bennett (1967, 1968) is discussed and extended to the replicated testing situation. An adjusted Bennett's statistic is proposed based on the Dirichlet-multinomial distribution. The conventional and adjusted Bennett's statistics are illustrated by a numerical example in product testing.     

COMPARISON OF METHODS FOR ANALYZING REPLICATED PREFERENCE TESTS

Preference testing is commonly used in consumer sensory evaluation. Traditionally, it is done without replication, effectively leading to a single 0/1 (binary) measurement on each panelist. However, to understand the nature of the preference, replicated preference tests are a better approach, resulting in binomial counts of preferences on each panelist. Variability among panelists then leads to overdispersion of the counts when the binomial model is used and to an inflated Type I error rate for statistical tests of preference. Overdispersion can be adjusted by Pearson correction or by other models such as correlated binomial or beta‐binomial. Several methods are suggested or reviewed in this study for analyzing replicated preference tests and their Type I error rates and power are compared. Simulation studies show that all methods have reasonable Type I error rates and similar power. Among them, the binomial model with Pearson adjustment is probably the safest way to analyze replicated preference tests, while a normal model in which the binomial distribution is not assumed is the easiest.     

CONSUMER ACCEPTANCE OF FOOD BARS

Increased use of conjoint analysis during the concept testing stage of food product development raises the question of whether conjoint analysis results translate into successful product development. Five food bar concepts from a previous conjoint analysis study targeted for the “Overall” panel, “Female” segment, “Male” segment, “Label Readers” segment and “Calorie Health Nuts” segment, were used for consumer testing. Standardized packaging was also developed to test elements not easily perceived from the product itself, i.e., low fat, low calorie and other nutritional information. The “Female #1 – commercial (Fiber One)” bar had the highest overall acceptance, 6.9 on a 9-point hedonic scale. Packaging significantly increased all ratings. Cluster analysis results were compared with segmentation from conjoint analysis. Similar results were found, showing there were clusters of consumers specifically interested in prototypes developed for specific conjoint analysis segments, which supports that conjoint analysis results translate into actual products.     

A THURSTONIAN VARIANT OF THE BETA-BINOMIAL MODEL FOR REPLICATED DIFFERENCE TESTS

The beta-binomial model is combined with a Thurstonian psychometric function to obtain estimates of the parameters of a distribution applicable to replicated difference tests. A method of estimating the variance of d'obtained from these tests is provided. A formula for determining sample size, which is composed of the number of trials (or panelists) and the number of replications, to determine d'is also given.     

EFFECTS OF A FIRE RESPONSE TRAIT ON DIVERSIFICATION IN REPLICATED RADIATIONS

Fire has been proposed as a factor explaining the exceptional plant species richness found in Mediterranean regions. A fire response trait that allows plants to cope with frequent fire by either reseeding or resprouting could differentially affect rates of species diversification. However, little is known about the generality of the effects of differing fire response on species evolution. We study this question in the Restionaceae, a family that radiated in Southern Africa and Australia. These radiations occurred independently and represent evolutionary replicates. We apply Bayesian approaches to estimate trait‐specific diversification rates and patterns of climatic niche evolution. We also compare the climatic heterogeneity of South Africa and Australia. Reseeders diversify faster than resprouters in South Africa, but not in Australia. We show that climatic preferences evolve more rapidly in reseeder lineages than in resprouters and that the optima of these climatic preferences differ between the two strategies. We find that South Africa is more climatically heterogeneous than Australia, independent of the spatial scale we consider. We propose that rapid shifts between states of the fire response trait promote speciation by separating species ecologically, but this only happens when the landscape is sufficiently heterogeneous.     

REPLICATED TRIANGLE TESTS: EFFECT OF FEED-BACK AND PRODUCT COMPARISON ON PERFORMANCE

The feed-back procedure consists of informing assessors of the quality of their response (correct or incorrect) after each triangle test. This procedure showed a contrasted effect according to assessors'detection abilities. A decrease in performance was observed for assessors who had low detection abilities whereas a slight increase was observed for assessors who had higher detection abilities. When the feed-back procedure is followed by a comparison by tasting of the two products, the increase in performance from the beginning to the end of the session is larger than that of both feed-back and control (no information) groups. We suggest that information inference from previous tests, which allows assessors to perform better at subsequent tests, is facilitated by the presence of a double information (feed-back and product comparison). This effect might be due to an attentional process allowing assessors to focus their attention on the difference between the two products. An attempt was made to model learning effect by variation of attentional weights.     

PREFERENCE MAPPING OF TEXTURE OF DULCE DE LECHE

The texture of 12 commercial samples of dulce de leche was characterized by means of texture profile analysis. Two sensory manual texture attributes (hardness and ropiness) were evaluated by a panel of 11 trained assessors. A panel of 50 consumers evaluated the texture acceptability of the samples using a 9‐point structured scale. Consumers showed highly significant different degrees of liking for the texture of the evaluated samples of dulce de leche. Clusters identified with Pearson's correlation coefficient showed opposite preference patterns and provided more useful information regarding market segmentation than clusters identified with Euclidean distances. External preference mapping and partial least squares regression showed that hardness was a driver of liking for one segment of consumers, whereas for the other one it was a driver of disliking. When all the consumers were considered, external preference mapping indicated that the ideal texture of dulce de leche would be intermediate, showing the importance of identifying preference patterns and suggesting that data averaging in consumer preferences might affect information recovery, and may lead to wrong conclusions. Different preference mapping techniques were compared; it was found out that when the relationship between acceptability and texture attributes was not linear, external preference mapping showed the best results.     

THE POWER OF SENSORY DISCRIMINATION METHODS USED IN REPLICATED DIFFERENCE AND PREFERENCE TESTS

Research on the power of discrimination methods in difference and preference tests has both theoretical and practical significance. Power is important to evaluate the sensitivities of tests and determine sample size. Ennis and Bi (1998, 1999) proposed the beta-binomial distribution to model replicated difference and preference tests with inter-trial variation and analyzed in general the power of the tests. In this paper, the power of discrimination methods for replicated difference and preference tests is discussed further. The equations for calculating power for methods based on the BB model are given. Examples with tables and charts for calculating and comparing the power of the methods are also given.     

REPLICATED SIMILARITY TESTING USING PAIRED COMPARISON METHOD

The present article discusses the replicated similarity testing using a paired comparison method. The “two one‐sided tests” (TOST) combined with a beta‐binomial model are proposed for this testing. Simulation studies provide evidence that the proposed testing is valid and reliable.     

鲫不同种系线粒体DNA物理图谱的构建

用１３种限制性内切酶对鲫鱼三个亚种共七个品系的线粒体ＤＮＡ进行分析,其中有９种酶在种系间或种系内产生限制性片断长度多态性,发现了１６个线粒体ＤＮＡ组合单倍型,通过双酶切分析,构建了１６个线粒体ＤＮＡ组合单倍型的１３种限制性内切酶的发点的物理图谱。     

BETA-BINOMIAL TABLES FOR REPLICATED DIFFERENCE AND PREFERENCE TESTS

Ennis and Bi (1998) discussed the beta-binomial (BB) model for replicated difference and preference tests. Based on the BB model, tables of the minimum number of choice responses to achieve significance at α≦ 0.05 are provided for replicated 2-AFC, Duo-Trio, 3-AFC and Triangular tests. The theory underlying the tables, how to use the tables, as well as some examples to illustrate their use are given. The tables can be used to evaluate the results of replicated difference and preference tests using forced choice methods.     

心外膜标测的技术与方法

本文简述了心外膜标测技术的发展与特点,报告了一种新型心外膜标测系统,其中使用了软基底６４点镀金电极和６４路放大器,标测结果用等时图和新颖的除极矢量图及除极矢量散点图表示。     

苹果Co基因的SSR标记定位(简报)

柱型苹果,其特征是节间高度短缩,腋芽萌发为大量的短枝,很少或无侧生延长新梢,呈自然单干形。柱型苹果几乎不需要修剪,非常适合于高密度栽植,可以极大地提高土地利用率。因此,柱型苹果是苹果株型育种的一个重要基因资源。然而,苹果是一类主要通过无性繁殖、基因组高度杂合、遗传背景十分复杂、童期漫长、且自交高度不育的多年生木本植物,通过常规的杂交育种来改良性状,不仅存在周期长、效率低的问题,而且会不可避免地将一些不利性状带到后代中去,增大了选择的难度。那么,若将分子标记辅助选择技术用于常规的杂交育种中,就可以有效地解决这些问题。筛选与性状紧密连锁的标记是实施这一方案的首要条件。同时,近距离分子标记的获得也是进行基因定位的工具,对最终实现基因的分离有重要意义。